Showing posts with label Wildlife Disease. Show all posts
Showing posts with label Wildlife Disease. Show all posts

Thursday, October 18, 2012

Back to the Backyard Denizens: Carnivores in Suburbia




I really like the picture of the Gray Fox above. 

I've been wanting to post this picture for a while, but didn't have a good reason to, until now. 

I think it nicely captures the idea of "Urban Wildlife", and a good way to get back into the blog mini-series I started on urban wildlife back in early 2011 (see The Gray Ghost posted on February 20, 2011; Backyard Denizens and Cronon's "The Trouble With Wildnerness" posted on March 15, 2011, and Return of the Backyard Denizens posted on June 10, 2011; and Aerial Backyard Denizens posted on January 10, 2012). 

I'm going to follow up on this theme with information gathered over a year ago.....while we lived in suburban North Carolina.
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I often put a camera out in the backyard when we lived there.  This began as an intermittent, when I remembered it, sort of thing. 

After a while it became interesting to the point where every night, with few exceptions, I'd set a camera out and pull it in the morning.  

Why did it become interesting, you ask?  

Thanks to the little critter with the big scientific name: Urocyon cinereoargenteus.


But....let me back up a bit.  As I mention in the Gray Ghost post referenced above, I first started seeing Gray Fox first-hand in our neighborhood back in Spring of 2010.  Their sightings became frequent enough that I was prompted to actually put a camera back there some time in early 2011 and started getting serious about recording my camera trapping records and visual sightings. 

My first pictures of Gray Fox in the back yard occurred in January of 2011 (see the Gray Ghost post referenced above).  Around this time, our family also saw a Gray Fox trotting along the back lot line at dusk as we played outside.  This led to a brief string of photographs, which ultimately dried up some time in February.  This short dry spell snapped a few weeks later, and March yielded two pictures: one on March 9...the other on March 21 (see above picture). 

Then the observations ground to a halt until about mid-May.
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On 5/11/2011, I took the dog out with me while programming the camera for the evening's deployment.  We walked slowly, and my attention was focused on the little plastic box in my hand.  Suddenly there was a tug on the leash, and I turned around to see the dog squatting in the middle of the yard.

Dang it, Sampson!, I said....knowing I'd have to go inside and get a bag to remove the pile o' shite, lest our daughter find it interesting the next day.

But...then the wheels started turning.  How could I both (a) avoid having to go all the way inside for a bag and (b) use this steaming pile to my advantage? 


The answer was clear!  I placed the camera on one of my daughter's kiddie chairs directly overlooking the dog's evacuation.  If anything was moving about that night, perhaps they'd come to investigate.  I'd used Sampson's "leavings" in this manner at my study sites with good results.  I'd even had success placing my cameras over an area where he had emptied his bladder in the yard (see pic at the top of this post).

However, the first night (post-fecal evacuation) was eventless! 

Bummer, I thought.  

But..still...why go all the way inside and get a bag to clean up this fine pile of animal attractant? 

I'll just keep an eye on my daughter when in the yard and make sure she doesn't step on it (-I know...I know...your minds are racing wildly...coming up with a million terrible father things to put in a comment on this post).  If I'm going to be lazy...then I better also be right about being lazy.  As such...failure was not an option!


On the afternoon of 5/13/2011, I even upped the ante.  We cooked burgers on the grill.  HUGE patties of succelent grass-fed beef acquired from a local farmer.  They were...to put it mildly...an absolute delight.  As an aside, let me just say: for those of you squandering your taste buds on hamburger from a giant corporate beef producer that you've picked up from your big box grocery store....you are missing out!  Seriously.  There is NOTHING like hamburger from a grass-fed cow that you buy at your farmer's market.

Anyways...that beautiful aroma wafted out for hundreds of yards from my grill, I'm sure.  Spreading the news that something good to eat might be here.

That night, a storm blew through the area.......one of many storms that plagued us that spring.  Seemed like we'd had one a week from the beginning of April to the end of May!  I put the camera out because I forgot we were supposed to get storms and I was excited about the new olfactory cues I had introduced into the backyard.  I didn't usually leave the backyard camera out during a lightning storm.  But when the thunder and lightning started, I shrugged and figured the camera wouldn't catch any critters. 

Perhaps it was the unintentional lures...perhaps it was the storm...who knows.  But...low and behold....I had a surprise on the camera the next morning.

Above:  The offending pile can be seen at the right in the field of view.  In the background is an Eastern Cottontail that triggered the camera before the storm hit.  Note: I don't, and never will, seriously attempt to draw carnivores into the yard with food or scent lures....but scent remains from Sampson's crap were all over out there anyways, so I figured I'd make it work to my advantage.


Above: My first backyard Coyote (Canis latrans) sniffing at my dog's home-brewed scent lure.  I'm not shocked by the fact that Coyotes were in this suburban neighborhood.  I'm more shocked that I hadn't gotten pictures of them before.  Too bad the camera lense was covered with moisture from the recent rain!


Above: The Gray Ghost (Urocyon cinereoargenteus) investigates things.  I've obviously seen these in the yard before.  What's strange is that it came by not long AFTER the coyote did.  I figured any evidence of the Coyote might scare them off.


Above: either a different, or the same, Gray Fox noses around near the camera again alittle later.

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A few nights after this, Sampson and I went through our usual routine for deploying the backyard camera.  This time, the cam quickly captured activity after our departure.

Above: Sampson and I leaving....

Above:  Note the difference in time-stamps.  This little fella slinks through less than 10 minutes after my dog and I passed the camera

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Unfortunately, about three days before the pictures above were taken (on May 15th) a rabid Gray Fox bit two people not less than a mile from where we live.  In one case, the fox first tangled with the person's dog while they were out on an evening walk.  When the owner tried to intervene with his foot, the fox moved on to him.  The second rabid fox incident did not involve a domestic dog.  This one occurred in the morning (8:30 am) rather than at night. 

On May 25th, someone in a neighboring county (about 25 minutes away) was attacked by a rabid Gray Fox while walking his dog.  He actually grabbed the fox by the neck after it bit him and threw it as far as he could.  The fox, however, did not give up so easily.  It apparently ran all the way back up the hill and attacked him again.  The man grabbed it once more, but this time was was able to secure it in a garbage can for animal control officers. 

Rabies was relatively common in that part of North Carolina.  For example, from January 1 to June 1, 2011 there had been four confirmed cases in our county alone.  Incidence of rabies may increase when potential carriers reach high densities, as the fox currently are in this general area.  HOWEVER, as Gehrt and Riley (2010) point out, there is not much information known on how living in urban areas alters wildlife disease dynamics for canids.

Don't take the wrong message from this post.  The risk of rabies from wild animals is low (see other posts regarding Wildlife Disease, including rabies here).  You're more likely to contract it from an unvaccinated domestic dog bite, according to many sources. 

Yet, given the number of fox we'd been seing around, I figured I'd start carrying a bit of personal protection when I took the dog out at night. 




Not that a bat would really help....especially considering I'm also dumb enough to wear shorts and sandals.  Even a small nip from a rabid animal can expose one to the virus and result in having to get the very unpleasant treatment.  Thus, to really protect yourself, you'd have to kill the rabid critter in one quick swing of the bat, before it's actually on you.  Even if we assume I'm deft enough to swing a bat so perfectly that it kills the rabid critter (a huge assumption), I almost certainly couldn't do it in one quick shot and without a scratch.  

But it at least made me feel a tad better. 

Also, as an aside, my dog wouldn't have been much help to me.  Despite his intimidating size and bark, he's not much of a brawler....but at least he's vaccinated.

Thankfully, the Gray Fox in our neighborhood didn't exhibit any signs of strange behavior.

They kept right on coming through the yard.

Above: our last Gray Fox picture on the camera trap for the month of May.


In fact, the sightings continued even without the aid of a camera trap! 

At 5 pm on May 26th, my wife called me at work and told me she had witnessed a Gray Fox crossing the road into neighbor's yard with something hanging out of its mouth (a prey item, although she couldn't tell what).  The area that our two yards made up was large...and wide open (no trees).  So the Fox was very exposed when he crossed here.  My wife asked if she should be concerned, given the recent rabies cases not far away.  I said that if the fox was out during the day and appeared to be wandering aimlessly, acting unafraid of people, or acting aggressive, then there should be concern.  If it was moving with a purpose, and away from human activity.....that was probably normal fox behavior.  Especially considering there were likely pups in the picture this time of year.  Perhaps this was the male bringing some food to the female while she nursed.  My wife then saw ANOTHER fox at about 8:30 pm that evening heading the same direction.

At 11 am on May 29th we saw the Gray running across the street and adjacent yards again.  We were all outside (including my dog), which didn't deter the little fox.  He moved with a purpose and was gone before the dog even got wind of him.  That night at about 10 pm, I took Sampson out and saw the fox's outline in the glow from a lone street lamp about 50 yds away.  He actually crossed through the area illuminated by the street lamp twice as I watched.  I say "he", because I'm still assuming it was a male who had a gal nursing pups nearby.  As such, he was on the move constantly to forage for himself and her.

Interestingly, despite the camera being in the yard every night....I didn't catch any more fox activity until the early morning of June 6th at about 2:14 am. 

Back then, I rarely used the video function on my cameras.  Mostly becuase it took up too much memory card space.  But, for a while, I felt like trying it with the backyard camera for a while...and got a nice clip of the gray.

The clip below was taken just off of the cement slab of my backporch (the camera is sitting on my daughter's little play picnic table).  So, this one came all the way up to the house, rather than skirting the back lot line. 

He takes sniff, wanders off in one direction and then cuts back across the yard a few seconds later.





In the early morning of June 14, 2011, the camera grabbed another video clip of a Gray Fox in our yard.  However, it wasn't a very good clip (about 1 second of fox, and 19 seconds of nothing) so I didn't post it.

June 16, 2011 (in the early morning), the camera took two pictures.  I had set the camera on a chair on the edge of the concrete slab of our back porch, facing out into the yard.

This is the second Coyote (that we know of) that passed through our yard.  He was on a mission, apparently, and the camera only recorded one blurry photo of him.


A few hours later, the little Gray Fox carefully sniffs his way through....following the same path as the 'yote.

On June 24 at about 12:51 am, a Gray Fox also meanders through the yard....but the picture isn't particularly good.

On June 27 at 10:00 am, I was out at my study sites when my phone rang.  It was my wife, and she was calling to report seeing fox pups for the first time!  She first saw an adult run across the road with four pups in-tow, as she pushed my daughter in the swing not 50 yds away.

On July 7, again at 10:00 am, I stopped home after field work to get some things together before heading out.  My daughter (not even three years old at the time) was standing by the window as I milled about next to her in the kitchen.  

Suddenly, I heard her say:

"Look Daddy!  A Fox!"  

Now, my daughter said stuff like this often (she had quite an imagination for a nearly 3 yr old).  I often heard things like "Look Daddy!  Creatures!"  or "Woody and Buzz want to talk to you!" and so on.  Because of that, I almost ignored her comment about the fox.  But couldn't help but take a look (I was impressed she remembered the word Fox at all, so I had to at least look).  

To my amazement, there was an adult Gray Fox running across the adjacent road and lawn!  On the opposite side of the road from the adult, I also saw one of the pups.  It ran part-way across the road, but turned abruptly and retreated back into the brush.  The adult sat completely exposed for a good thirty seconds looking back at the juvenile.  Eventually, a car came along and the adult casually trotted off in the opposite direction.

A half hour later, Dave had come by.  We were all going somewhere as a group (Dave, me, my daughter and wife).  Just before we left, my daughter saw the fox again with the juvenile.  She turned to Dave and said "Look a Fox, Dave!  The big fox is looking for the little one!"

Now, I can't help but brag a little about my daughter.  

Prior to that day, she'd only gotten one fleeting glimpse of a fox in the backyard...and maybe a few black and white IR pictures from my cameras.  Not only did she see the fox (which was more than 50 yds away), but she remembered it was a fox AND told me and Dave!  This on top of the fact that she was not even three years old at the time.  

What more could a father ask for?  :)

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Interestingly, the pictures of them at my more "natural" study sites had ceased as of March.  They must have been tending to young some where on-site that didn't happen to be close to the cameras.

There were also no more accounts of rabies in the area to my knowledge during that spring/summer..... 

I miss those little canines.  They are much more rare up here in the midwest and I don't get the pleasure of seeing them anymore.

Further Notes on Urban Gray Fox and Coyotes:

Coyotes (I cite a variety of sources below, but have taken liberally from the outstanding review by Gehrt and Riley, 2010):

According to Bekoff and Gese (2003) Coyotes are one of the most-studied canids in North America.  Despite this, as Gehrt and Riley (2010) point out, relatively little of this work has focused on Coyotes in urban or suburban settings.  The most detailed work on this subject probably comes from Stanley Gehrt and his colleagues, who have focused on Coyotes in very urban areas in or around Chicago, Illinois.  Furthermore, Seth Riley has worked on urban Coyotes in southern California, and Jonathan Way has done considerable research in Cape Code, Massachussets.

Population Density and Survival-. Densities of Coyotes in urban/suburban landscapes have generally been found to be higher than in rural settings.  As Gehrt and Riley (2010) review, urban density estimates in a site from southern California (a site considered "urban-adjacent") were 2.4-3.0 per square kilometer.  Increased food sources (i,e, trash and domestic fruit) may be contributing factors, as "anthropogenic food items" were 14-24% of the diet of these coyotes.  In the greater Chicago area, density estimates of 2 to 6 coyotes per square kilometer were calculated.  On the other hand, Bekoff and Gese (2003) review density estimates in a variety of more natural settings and report numbers of 0.1-0.9 coyotes per square kilometer and one fall estimate of 1.5-2.3 / square kilometer.  Survivorship is generally high in urban areas...with survival estimates being comparable to un-hunted or un-trapped populations in natural settings.  Yet despite high survivorship, threats to survival of urban coyotes still exist.  For example, vehicle collisions represented 62% of all Coyote mortality in the greater Chicago area.  In southern California, over a nine year period, 27% of coyote mortalities were the result of anticoagulant rodenticide poisoning (perhaps picked up by eating dead or dying rodents that have consumed the rodenticide).  In the same study, vehicles were found to be the cause of 51% of the coyote mortalities (Riley et al. 2003).

Activity and Habitat-.  Several studies have confirmed that Coyotes in urban areas shift their activity to be mostly nocturnal (rather than crepuscular or diurnal).  This is largely believed to be because it allows urban Coyotes the opportunity to avoid humans during the day, while also making it possible to move around when the volume of traffic is lower.  This would explain the fact that the pictures I have collected of them both in my yard and at my study sites are all in the evening or very early morning.  Furthermore, studies that have occurred in a variety of geographic locations have found that the habitats selected by urban coyotes usually involve a small natural island or natural buffer, which is used as the core of the home range (Riley et al. 2003, Gehrt et al. 2009).  Their territories then include forays into the adjacent fragmented urban landscape from this central natural location.

Urban Diet and Threats to Pets or People-. Urban Coyotes have slightly different diets than their counterparts living in more rural landscapes.  In the Chicago area, for example, an important dietary stable were the eggs and hatchlings of Canada Geese (Branta canadensis).  These have become very abundant around a variety of water sources, including man-made stormwater retention ponds, making them an easy food source.  Coyotes are also an important predator of urban white-tailed deer fawns.  As Gehrt and Riley point out, this may be a useful means by which urban deer are managed, given the fact that hunting may not be allowed within city limits.  Domestic cats that allowed to roam freely and feral cats also fall victim to Coyotes, a phenomenon that increases in frequency in residential areas.  This has been correlated with higher songbird densities by Crooks and Soule (1999).  Urban coyotes may also attack domestic dogs.  According to Gehrt and Riley, most attacks are on smaller breeds (e.g., Jack Russel Terriers, Shih Tzus), but a group of coyotes may attack larger domestic dogs, as well (Gehrt and Riley 2010).  Attacks appear to peak during the mating season (December-February) and in April when pups are born. 

Attacks on humans are known to occur.  White and Gehrt (2009) reviewed 142 coyote attacks on humans and place them in the following categories.
  • Predatory (37%), primarily involving children
  • investigative (22%), including a a minor bite, or nip, usually directed towards adults
  • pet-related (6%)
  • defensive (4%), usually directed towards adults
  • due to rabies (7%), usually directed towards adults
Attacks on people possibily involve some level of habituation, but this is poorly understood in urban coyotes (Gehrt and Riley 2010).  Coyotes are known to actively avoid humans most of the time, and the context surrounding habituation of urban coyoes has not been rigorously investigated.  Yet, habituation (much like attacks on humans) are not common.  For example, of 150 coyotes followed with radio telemetry in the Chicago area, only five adopted problematic behaviors (Gehrt and Riley, 2010). This included taking frequent advantage of food sources in residential yards, such as birds at bird feeders.  Yet, as Gehrt and Riley point out, seeing Coyotes near residential homes eating trash, fruit, pets, or being active during the day should not be automatically considered a sequeway to attacking humans.  Instead this is equally indicative of the behavior exhibited by a "flexible" generalist predator.  Instead, concern should be raised when certain types of aggression are shown, such as failing to run from humans, or growling and barking in the presence of humans.

Gray Foxes:

Surprisingly little research has been conducted on urban/suburban Gray Fox.  According to Riley and White (2010), the most detailed studies come from California (Riley 2001, Riley 2006 and Riley et al. 2004), and New Mexico (Harrison 1997, but also see Kapfer and Kirk 2012).  Farias et al. (2005) also radio tracked Gray Fox near Los Angeles, but the tracked animals did not use urban or suburban areas.  Riley and White (2010) indicate that Gray Fox cannot stand landscapes inhabited by humans as well as other carnivores.  In fact, Harrison (1997) suggested that they would only withstand a housing density of 1 house/3.1 acres (or 50-125 residence per km-squared).  Geographical Information System (GIS) analysis of our neighborhood in NC revealed a much greater density of buildings (237-347 buildings/km squared) then Harrison suggested Gray Fox would tolerate (Kapfer & Kirk 2012).  However, we also have some pretty sizeable woodland buffers in our area, which may explain why our Gray Fox withstand heavier development than in Harrison's (1997) study (Kapfer & Kirk 2012).

Use of Urban Areas and Periods of Activity -.  The work in California found that most of the radio-tracked Gray fox (which were associated with a national park north of San Francisco) used urban areas only sparingly.  This use included forays into developed areas during the evening.  Harrison's work in New Mexico found that, although Gray Fox avoided urban areas during the day, they actually selected for them at night.  This seems similar to what I've seen this species doing in NC, with the exception of the time period when the males were bringing food for nursing females.   In California, vehicles are a known source of mortality for urban Gray Fox...and I'd seen at least three dead on the roads near our home from 2010 to 2011. 

Diet and Threats-. Interestingly, food associated with people was not a major portion of fox diets in the previously mentioned studies.  We don't leave dog food outside, and there's really no other food for them to get into around our house, aside from maybe the trash....but I'd never noticed any problems there.  I had found a dried up roadkilled squirrel husk in the backyard the morning after witnessing two Gray Fox run along the lot line one evening.  The most commonly consumed food in the diet of urban Gray Fox are small rodents (Riley and White 2010).  Attacks on pets and people are apparently rare.  Probably the biggest threat in this regard is possible attacks by rabid individuals.

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I'm glad that I finally came back to this topic of urban wildlife (even though it was after we had moved from our suburban home).  A few of my "ongoing" post topics have been in need of revisitation for some time.  I have other Backyard Denizens from NC that I will report on in the future.


Literature Cited:

Bekoff, M. and E.M. Gese. 2003. Coyote (Canis latrans). In G.A. Feldhammer, B.C. Thompson, and J.A. Chapman. (eds.). Wild Mammals of North America: biology, managment and conservation.  2nd Edition. Johns Hopkins University Press.

Farias, V, T.K. Fuller, R.K. Wayne, and R.M. Sauvajot. 2005. Survival and cause-specific mortality of grey foxes (Urocyon cinereoargenteus) in Southern California. Journal of Zoology 266:249-254.

Gehrt, S.D., C. Anchor, and L.A. White. 2009. Home range and landscape use of coyotes in a major metropolitan landscape: coexistence or conflict?  Journal of Mammalogy 90:1045-1057.

Gehrt, S.D, and S.P.D Riley. 2010.  Coyotes (Canis latrans). In S.D. Gehrt, S.P.D. Riley and B.L. Cypher (eds.). Urban Carnivores: ecology, conflict and conservation.   Johns Hopkins Press.

Harrison, R.L. 1997. A comparison of gray fox ecology between residential and undeveloped rural landscapes. Journal of Wildlife Management 61:112-122.

Kapfer, J.M., and R.W. Kirk. 2012. Observations of gray foxes (Urocyon cinereoargenteus) in a suburban landscape in the Piedmont of North Carolina. Southeastern Naturalist 11:507-516.

Riley, S.P.D. 2001. Spatial and resource overlap of bobcats and gray foxes in urban and rural zones of a national park.  In A. Woolf, and C.K. Nielsen (eds.).  Proceedings of a Symposium on the Ecology and Management of Bobcats. Illinois Department of Natural Resources, Champaign.  (NOTE: I could not find a copy of this report and cited the interpretation of it given by Riley and White, 2010).

Riley, S.P.D. 2006. Spatial ecology of bobcats and gray foxes in urban and rural zones of a national park. Journal of Wildlife Management 70:1425-1435.

Riley, S.P.D., R.M. Sauvajot, T.K. Fuller, E.C. York, D.A. Kamradt, C. Bromley, and R.K. Wayne. 2003. Effects of urbanization and habitat fragmentation on bobcats and coyotes in Southern California. Conservation Biology 17:566-576.

Riley, S.P.D., J. Foley, and B. Chomel. 2004. Exposure to feline and canine pathogens in bobcats and gray foxes in urban and rural zones of a national park in California. Journal of Wildlife Diseases 40:11-22.

Riley, S.P.D., and P.A. White. 2010.  Gray Fox (Urocyon cinereoargenteus) in Urban Areas.  In S.D. Gehrt, S.P.D. Riley and B.L. Cypher (eds.). Urban Carnivores: ecology, conflict and conservation.   Johns Hopkins Press.

Saturday, July 9, 2011

Week's End Survey Round Up VII: Copperheads and Cyst-laden Salamanders

Much like last week, we had a lot of rain and wet to deal with during our surveys.  As you can see from the pictures above, a bunch of standing water and dripping vegetation.

Interestingly, we didn't catch as much this week, as we did last week.  I imagine that because it had been so dry for nearly a month prior to the rains last week....once it got wet, the critters exploded out of hiding and became very active.  Now that the wet conditions are sort of old hat, they aren't quite as active.

Regardless, we still caught some cool stuff....but nothing really new.
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Another nice sub-adult or, perhaps, young adult Eastern Ratsnake (Pantherophis alleghaniensis).  We carry a bucket of our gear with us in the field.  Every time we get a critter to deal with, we set up a little workstation to collect appropriate data.  One person takes measurements and yells out numbers, while the other records.  It works out pretty well.  Often, a back-pack of gear is a good option too...but I sort of like the bucket (I can fit more in it and whatever I put in stays dry).  It can be a bit cumbersome, though.


Above: our bucket O' gear that we carry with us in the field.  Also you can see the handle of the potato rake, which is the most versatile and important tool a field herper can have!  It will flip rocks, turn logs, act as a walking stick, and help balance you when rock-hopping across streams.  It can also be used to carry funnel traps with venomous snakes AND act as a snake hook for venomous snakes, if necessary. 

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The Copperhead (Agkistrodon contortix).  I just can't get enough of Copperheads.  I'll post pictures of every one I see.  They are absolutely beautiful.  This little juvenile was in our grassland/old field drift fence after a few days of heavy rain.  Could have been after some frogs that crawled in....who knows.

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The Box Turtle in the funnel trap.  Well, it wasn't quite in the funnel trap, I guess.....  But it sure seemed like it was trying to get caught!  When we found it, the turtle had been meandering along the fence right up to where entrance to the funnel (which it couldn't fit into, as you can see below).

This adult male ended up getting marked number 13 and left to go on about his business.


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The cyst-laden Two Lined Salamander (Eurycea cirrigera).  This week Dave actually randomly saw two of these guys wriggling around in the leaf litter near our fences and grabbed them.  A consequence of the more moist conditions out there these days is that salamanders hang out closer to the surface of the ground.

After giving one of them a little scrutiny, we noticed these white dots that appeared to be just below the surface of the skin of this little guy's front legs.  I'm fairly positive these are the larval stage of some type of parasitic flatworm.  Either a trematode (a.k.a. fluke) or a cestode (a.k.a. tapeworm)...probably the former.  While I can't be 100% sure of this, because we didn't want to necropsy the animal to be sure, I've worked with two parasitologists in the past.  Both were involved in research on amphibian parasites, and these little critters pick up alot of invertebrate baggage throughout their lives.


The lifecycles of parasitic flatworms are fascinating.  Particularly those considered digenetic trematodes.  These may have two or more larval stages that will exist in as many hosts...and an adult stage that occurs in yet a third host....throughout their lifecycle.

Let us begin with a simple example: a group of adult flukes living in the intestines of a predatory wading bird (like a Great Blue Heron).  The flukes in the intestines reproduce and shed eggs...these eggs then exit the Heron when it defecates.  In this way, thousands of eggs are broadcasted into the environment.  Herons often defecate in or near water...when these eggs hit the water, they hatch into their first larval form, which is a tiny free-swimming stage called a miracidium.  The miracidium is microscopic and ciliated.  It uses these cilia (little hairs) to swim around in the water like a paramecium.   They are on the look-out for an appropriate invertebrate host, which is often an aquatic snail of some kind (the first intermediate host for these critters is usually an invertebrate).  When the find a snail, they burrow into their tissues and start to develop.

After a period of development inside of the snail, the parasite is shed and returns to the water as a form called a cercariae. The cercariae are basically microscopic and look almost like tiny little tadpoles..little tail and all.  Now these little guys also start swimming around the water looking for a host (called a second intermediate host)..but this time they don't look for a snail.  This time they're after a cold-blooded vertebrate (often a fish or larval amphibian).  The cercariae penetrates the skin of the larval amphibian, burrows into its muscle and encysts into a resting stage called a metacercariae. I *believe* it was the metacercarial cysts that we saw on the arms of the salamander pictured above.

A larval parasite can remain as a metacercarial cyst for a fairly long period of time (what this period of time is, on average, I don't know).  Basically, it bides its time until an appropriate terminal host consumes the second intermediate host.  The terminal host is usually a predatory bird or mammal...but may also be a larger fish, snake, turtle, etc..  So...for example...a heron eats an infected fish...or an infected tadpole/frog.  When that infected muscle is consumed, the metacercariae pops out of the cyst in the terminal hosts stomach and becomes an adult fluke.  Once it is an adult, it can reproduce in the intestines and start generating its own eggs that can then be shed in the feces of the heron and the lifecycle starts anew!

Click here for more information on how these parasites may cause malformations in amphibians.  This is the website of Dr. Pieter Johnson at the University of Colorado.  He has studied digenetic trematodes of amphibians for some time.  There is more information on the lifecycles and also a picture depicting a lifecycle at this link.

I've given you only one example.  Certain parasite species may have more or less hosts....these hosts may be of a variety of critters, or specific to one or two.  Depending on species, adult parasites may end up in places aside from the intestines, such as the lungs, the bladder, the stomach, the esophagus and so on.  And any one host can carry many individuals of many different species of parasite at any given time!

Very fascinating and very complicated life cycle for such a small little critter.  I'll say it again, the importance of wildlife diseases cannot be overstated!

Wednesday, June 8, 2011

Now that's one huge pile of 'yote crap!.... with comments on wildlife diseases


Above: the massive pile of steaming canine crap found on May 6, 2011. Compare to the pictures below.  Note: the key in most of these pictures is roughly three inches long.


Could be from a big domestic dog....I supose you may say. 

True, I respond, but it has hair in it.

Ok....perhaps a farm dog was eating roadkill, you counter.

Possible, I consider, but it also has some sort of fruit husk or seed in it, and coyotes eat alot of that type of stuff.

Hmm, you ponder.  Well, domestic dogs might eat that too.  My dog will eat carrots sometimes.

A-huh.  Well, when we broke the scat up with a stick it was full of tape-worm proglottids, I mention.

Ew!, you cringe.  I hope that wasn't a domestic dog!

Me too!  Otherwise there's an owner somewhere that will be very unhappy when they find their dog scooting its butt across the carpet, only (on closer inspection) to find a tapeworm sticking out of its rear-end.

Alright...now I'm just being needlessly graphic.  The perks of having two mentors with backgrounds in Parasitology, I guess.

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The scat above was placed near a trail intersection at one of my sites.  Last year at approximately the same time (April 21, 2010), I saw another rather large pile of scat at about the same location (isn't it great to have a library of poop pics on one's computer?).  It also had alot of hair in it...and some seeds or grain of some kind.

Above: the large canine scat found on April 21, 2010.


Compare the scat examples above to one I found in March of this year (below).  This picture depicts Coyote scat that is a size I am more used to seeing.



Notes on Coyote parasites:

The importance of understanding wildlife parasites and disease cannot be overstated.  Studying wildlife diseases and parasites is not particularly glamorous, especially compared to stuff like radio telemetry or camera trapping.  For example, macro-parasite research may involve sifting through excrement under a microscope or analyzing sections of intestines and other organs post-mortem.  Yet, parasites and diseases are an important source of mortality for wildlife.  They can potentially regulate stable populations, or be a major conservation concern for rare species.  There is also the possibility that wild animals may transmit diseases to pets and livestock.  Finally, wildlife diseases can result in zoonosis.  Zoonoses are infectious diseases that jump from non-human animals (wild or domestic) to humans, and back.  Thus, the study of parasites and diseases is incredibly relevant to wildlife management, conservation and human health.   

Wild Canids potentially suffer from, and carry, many infectious agents (ticks, lice, fleas, tapeworms, roundworms, viruses, etc.).  Woodroffe, et al. (2004) give a very nice overview of the general topic of infectious diseases that plague wild canids.  They review information that suggests wild canids may be particularly vulnerable to disease outbreaks, which they suggest has to do with aspects of their ecology. 
  • A high trophic status (feeding postition in the food chain): because canids are often higher on the food chain, they are exposed to diseases carried by prey.  Tapeworms and flukes, for example, are often contracted by a predator when it consumes the muscle of an infected prey animal.
  • Intolerance of other carnivores that may be competitors:  territorial conflict or competitive interactions among wild canids or other carnivores may increase the likelihood of contact with infected animals.
  • Living in social groups: this provides another avenue for contact with potentially infected individuals that a solitary animal does not face.  Canids in social groups will often lick and groom eachother.
  • Communication via feces and urine that may be infected: investigating or scent rolling in the scat of a sick individual may be a potential route for infection.
  • The fact that domestic dogs are also canids: as the authors point out, most domestic dog populations are regulated by humans, not disease.  Where there are large populations of people, there are usually large populations of dogs.  These domestic dogs can act as a source (or resevoir) for infectious diseases that may plague wild canids (remember also that in some regions of the world, "domestic" dogs are not vaccinated, and often allowed to roam freely). 
There has been a fair amount of published literature on the topic of diseases that impact canids, particularly as it pertains to Coyotes.  To my knowledge, the first thorough review of Coyote parasites and disease is Gier et al. (1978).  This is a chapter is Marc Bekoff's Coyotes: biology, behavior and management...a very good introduction to the basics of Coyote ecology.  Not a book for the lay-person, but an an excellent scientific reference for this species.  Since then a number of other papers on the subject have been published.

Examples of External Parasites that Affect Coyotes

Mange.-  According to Gies et al. (1978) there is potential for both sarcoptic mange and demodectic mange in Coyotes.  Sarcoptic mange is the result of a mite (Sarcoptes scabei) that burrows into the skin and lead to an acute itch.  Infected coyotes bite, scratche and rub at this itch (perhaps to the point of hair removal), and secondary bacterial growth can result.  Demodectic mange is the result of a different species of mite (Demodex canis) that feeds on the hair follicles, rather than burrowing into the skin.  This can also result in "hairless" coyotes.  Both of these parasites have apparently given rise to many current "chupacabara" reports.


Ticks.- Coyotes can become infested with any number of tick species.  These usually attach on the face or ears, where the hair is short.  According to Gies et al. (1978) only a few species of tick appear to actually "thrive on coyote blood".   Although coyotes have been found to carry the antibodies for Rocky Mountain Spotted Fever, a disease transmitted by ticks in the genus Dermacentor (such as the Long-Star Tick), they apparently do not exhibit clinical symptoms of the disease.

Due to urban/suburban sprawl and agricultural expansion, the potential for contact between humans, domestic animals and wildlife is on the rise.  This trend is likely to increase.  As humans alter landscapes, it is possible that we enhance habitat for species that may carry disease.  For example, habitat fragmentation has created an extensive network of "edges" across the landscape (areas where two habitat types meet, in this case where natural and altered habitats meet).  Edge habitats are conducive to some species, like White-tailed Deer (Odocoileus virginianus) and various rodents, which can carry the ticks that spread lyme disease. 

Information on Lyme Disease, which is spread by the black-legged or deer tick (Ixodex scapularis), and coyotes is sparse.  Several studies have found a link between deer densities and prevalence of the black-legged or deer tick (Rand et al. 2003).  The tick actually carries the bacterium that causes Lyme Disease internally, but the deer gives the tick a place to live, feed and reproduce (the deer is, therefore, considered a vector).  With higher deer densities comes more hosts for ticks, which can increase the prevalence of Lyme Disease.  For example, Rand et al. (2003) found that relatively few ticks were found on white-tailed deer when deer densities were less than 7/km-squared. 

The same group of researchers published another very interesting study in 2004 that focused on Monhegan Island (off the coast of Maine; Rand et al. 2004).  White-tailed Deer had been introduced to this island in 1955 and had experienced a large population increase over the following three decades.  In the 1980s, deer densities were estimated to be at 37/km-squared!  At that time, ~13% of the year round human residents of the island had contracted Lyme disease.  Estimates of tick desnities in the early 1990s were 6-17 adults ticks/ hectare, with 24-41% of these ticks carrying the Lyme disease bacterium.

From 1996-1999 all deer were removed from the island.  For a very brief period immediately after the removal of deer (fall 1999), tick densities and prevelance of ticks infected with the bacterium rose substantially (28 ticks/hectare and 75% infection rate with Lyme Disease).  But wait for it!  By the summer of 2003, these numbers had dropped dramatically, with tick densities estimated at a mere 0.67 ticks/ hectare and 29.4% infection rate.  Concurrently, Rand et al. also monitored tick densities and infection rates on a nearby reference island still populated by deer and found that tick densities had continued to gradually increase during this same time.

Lyme Disease sucks.  Trust me.  Anything that can reduce the potential for contracting it when in the outdoors is A-OKAY in my book.

Examples of Internal Parasites:

Tapeworms-. Tapeworms are a particularly common parasite in the intenstines of coyotes, with some 65-90% of coyotes examined being infected in some cases (Gies et al. 1978).  The most commonly reported tapeworm species in coyotes is Taenia pisiformes.  The larval form of these tapeworms encysts in the muscles of prey animals....such as rabbits, which are a primary prey species for coyotes.  When a coyote eats an infected rabbit, they ingest the cysts in the rabbit muscle.  The cysts then develop into adult tapeworms in the intenstines of the Coyote.  This adult tapeworm grows (sometimes it reaches 4 -10 inches in length), and as it grows it produces more and more segments called proglottids.  These proglottids each carry hundreds or thousands of tapeworm eggs.    When an infected coyote excretes, mature proglottids break off of the tapeworm's main body. These proglottids are then evacuated from the intestines with the excrement.  These proglottids eventually open and eggs get on the grass/vegetation near where the coyote left the scat.  Geis et al. (1978) reported finding up to 110 of these adult worms in an individual coyote....each producing many proglottids (segments)....and each proglottid producing thousands of eggs.  That's alot of tapworm eggs being broadcasted into the environment.  Rabbits that eat the vegetation pick up the eggs...which eventually lead to larval tapeworm cysts in the muscles of the rabbit and the parasite lifecycle starts a-new.

The canine tapeworm that likely poses the most serious threat of mortality to humans is Echinococcus granulosus.  The eggs can be accidentally ingested by humans from close contact with infected dogs.  The larval form of this parasite in people can result in a large concentration of larval tapeworms that collect in a structure called a hydatid cyst.  The cyst can be the size of a golf ball or even grapefruit, and typically forms on the liver, kidneys or brain.  Should this cyst rupture, release of this large volume of foreign proteins into the body at once may result in mortality from anaphylaxis.  Removal of the cyst can only be done through surgery.  The incidence of coyotes infected with this particular tapeworm is (apparently) not high.

Tapeworms, and other internal parasites like flukes, adversely affect coyotes in a variety of ways.  The tapeworm nourishes itself from tissues and other digested materials in the coyote's intestines....this obviously draws away nourishment/nutrients that would otherwise go directly to the coyote.  If tapeworm loads become too heavy, they can actually cause a blockage in the intestines.  They may also cause internal irritation or result in secondary infections in the instestines.

Roundworms.- Any number of roundworms, such as hookworms, are found in the gastrointestinal system of coyotes.  The hookworm Ancylostoma caninum attaches to the intenstinal lining and feeds on blood/tissue.  These worms may migrate around in the intenstines and each time it finds a new feeding location, it potentially leaves an open wound from the spot it was previously feeding at.  A study of coyotes in the Gulf Coast of Texas found that every individual analyzed may carry up to 250 hookworms each (Mitchell and Beasom, 1974).  This obviously can lead to internal bleeding, and secondary bacterial infections.

Filarlial worms, the most infamous of which being Dirofilaria immitis (the canine heart worm) infect coyotes.  The infection rate of canine heart worm in wild coyotes varies considerably (from 1-36% infection rate depending on location; Geis et al. 1978).  A study in Illinois found a state-wide prevalence of 16% infection in wild coyotes (Nelson et al. 2003).  This same study found that the heart worm infections (i.e. the number of worms present per individual coyote) were rarely heavy.  Furthermore, although low body weight and kindey fat (both indicators of overall health) were not correlated with heart worm infections among coyotes, infected females did have a lower reproductive success than uninfected females.

Viral Infections-.  The most well-known wildlife viral disease is probably rabies.  Until the late 1980s, rabies was recorded only sporadically in coyotes.  At that time, however, a substantial outbreak of rabies in coyotes ocurred, that also spread to domestic dogs, in Texas (Clark et al. 1994). Coyotes are not often considered one of the main host species for rabies....this is usually reserved Raccoons, Skunks, Foxes and also Bats, which accounted for 91% of all rabies cases during 2000.  Domestic species accounted for 7% of the rabies cases in that year, and the remaining 2% of cases were the result of 13 other mammal species (one of which was the Coyote; Krebs, et al. 2003).  Over a 40 year period (1960-2000) a total of only 2,851 cases of rabies were reported from animals OTHER THAN Raccoons, Skunks and Foxes (Krebs et al. 2003).  This represented only 1.3% of the >215,000 cases of animal rabies.  Of these, 22% of the cases included coyotes.  So...a pretty low incidence.

Distemper is another disease that affects coyotes.  A survey of 228 coyotes sampled in Texas revealed that 56% tested seropositive for distemper (Guo et al. 1986).  Unlike rabies, canine distemper does not affect humans....but it can be a threat to domestic dogs.  During a four-year study in Colorado, 57% of 72 sampled coyotes tested positive for distemper (Gese et al. 1991).

Probably the most complete treatise on wild animal diseases to-date is Williams and Barker (2001).  Check it out for further information.

Oh...and to be safe...never actually touch any wildlife scat that you encounter in the wild (like I need to tell you this).  :)


Literature Cited

Clark, K.A., S.U. Neill, J.S. Smith, P.J. Wilson, V.W. Whadford, G.W. McKirahan. 1994. Epizootic canine rabies transmitted by coyotes in south Texas. Journal of the American Veterinary Medicine Association 204:536-540.

Gese, E.M., R.D. Schultz, O.J. Rongstad, and D.E. Andersen. 1991. Prevalence of antibodies against canine parvovirus and canine distemper virus in wild coyotes in southeastern Colorado. Journal of Wildlife Disease 27:320-323.

Gier, H.T., S.M. Kruckenberg, and R.J. Marler. 1978. Parasites and diseases of Coyotes.  In Coyotes: biology, behavior and management. M. Bekoff (ed.). The Blackburn Press.  Caldwell, NJ.

Guo, W., J.F. Evermann, W.J. Foreyt. F.F. Knowlton, L.A. Windberg. 1986. Canine distemper virus in coyotes: a serologic survey. Journal of American Verterinary Medical Association 189:1099-1100.

Krebs, J.W., S.M. Williams, J.S. Smith, C.E. Rupprecht, and J.E. Childs. 2003. Rabies among infrequently reported mammalian carnivores in the United States, 1960-2000. Journal of Wildlife Diseases 39:253-261.

Mitchell, R.L. and S.L. Beasom. 1974. Hookworms in south Texas coyotes and bobcats. Journal of Wildlife Management. 38:455-458

Nelson, T.A., D.G. Gregory, J.R. Laursen. 2003. Canine heartworms in coyotes in Illinois.  Journal of Wildlife Diseases 39:593-599.

Rand, P.W., C. Lubelczyk, G.R. Lavigne, S. Elias, M.S. Holman, E.H. Lacombe, and R.P. Smith Jr. 2003. Deer density and the abundance of Ixodes scapularis (Acari: Ixodidae). Journal of Medical Entomology 40:179-184.

Rand, P.W., C. Lubelczyk, M.S. Holman, E.H. Lacombe, and R.P. Smith Jr. 2004. Abundance of Ixodes scapularis (Acari: Ixodidae) after the complete removal of deer from an isolated offshore island, endemic for Lyme Disease. Journal of Medical Entomology 41:779-784.

Williams, E.S. and I.K. Barker. 2001. Infectious Diseases of Wild Mammals (third edition). Iowa State University Press.  Ames, IA.

Woodroffe, R. S. Cleveland, O. Courtenay, M. K. Laurenson, and M. Artois. 2004. Infectious disease: infectious disease in the management and conservation of wild canids.  In Biology and Conservation of Wild Canids, D.W. Macdonald and C. Sillero-Zubiri (eds.).  Oxford University Press.