2016 Fall

Huggin’ Trees by Design

By Tim Ross (Own work) [Public domain], via Wikimedia Commons

By Tim Ross (Own work) [Public domain], via Wikimedia Commons

How do you survive if you’re not the most dominant canine in an area? If you have to share space and potential food with your faster and sometimes much larger cousin, how do you and your kin thrive day in and day out? These are questions the gray fox, Urocyon cinereoargenteus, must answer.

The common gray fox is a crepuscular and nocturnal canid whose home range averages around 1.5 square miles. This range contracts during the spring when they mate and have pups and then expands during the fall while they search for food. Their diet, like both red foxes and coyotes, consists of small mammals and even birds. Unlike other canids, the gray fox’s digestive system is better equipped to handle much more fruit.

In many parts of the southeast, including Statesville, gray foxes live with both red foxes and coyotes. Not much is known about how red foxes and gray foxes divide habitat in areas where they overlap. What is known is that red foxes seem to prefer more open terrain while gray foxes stick to the woods. it’s certainly possible that these two species use time-share strategies to avoid interactions.

Having to share space and resources with coyotes, however, could cause major, or fatal, problems for the foxes. Coyotes have been implicated in the decrease of red fox populations in certain areas (Cypher 1993). However, gray fox populations do not seem to be impacted as much by the larger coyote. Our small data set from greenway patches seem to support the idea that gray foxes tolerate coyotes better than red foxes. The following shows the number of pictures of each species we have collected from two camera traps from August to December during both 2015 and 2016:

                               Camera A             Camera B
Coyotes             25                         10
Gray fox            24                           2
Red fox                1                           2

Is the explanation just that the diets of gray foxes and coyotes are different or is it that gray foxes avoid coyotes spatially and/or temporally?

Both Cypher (1993) and Neale and Sacks (2001) found that there was actually a high dietary overlap among coyotes and gray foxes year-round. The implication is that this means, more than likely, that there is interspecific competition when they live in the same area. Neale and Sacks (2001) also used scat analyses to determine that gray foxes did not avoid coyotes in space. Our data (Figure 1) suggest that gray foxes don’t avoid coyotes in a temporal (time) dimension either.

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Figure 1. Gray fox versus Coyote

The answer to how gray foxes avoid coyotes seems to be found in their evolutionary past. Gray foxes were the first canid to diverge from the rest of the canid family. They are a primitive species that branched off from the rest of the canids around ten million years ago (Lindblad-Toh et al. 2005). As a matter of fact, there is scientific support that states that the gray fox should not even be considered a canine or a vulpine (red fox). The gray fox is what geneticists call a basal canid, meaning it represents an ancient lineage.

Gray fox climbing in Statesville

Gray fox climbing in Statesville

As a result of this ancient lineage, the gray fox has many unique characteristics. Some features are only shared with another ancient species, the raccoon dog (Nyctereutes procyonoides). Gray foxes have hooked claws and the ability to rotate their forearms. This, coupled with the fact that they have the shortest leg-to-body ratio of any wild canid, allows them to easily hug tree trunks or branches and climb. Ecologically, they are more like cats. When pursued, gray foxes are not really interested in running. They would rather scamper up a tree. It’s this ability that helps them minimize conflict with coyotes.

Next time you are out in the forest, take the time to look up into the trees. You may get a peek at one of these cat-like dogs.

Gray fox foraging

Gray fox foraging


Cypher, B. L. 1993. Food Item Use by Three Sympatric Canids in Southern Illinois. Transactions of the Illinois State Academy of Science, 86: 139-144.

Lindblad-Toh et al. 2005. genome sequence, comparative analysis, and haplotype structure of the domestic dog. Nature, 438: 803-819.

Neale, J. C. C. and Sacks, B. N. 2001. Food habits and space use of gray foxes in relation to sympatric coyotes and bobcats. Canadian Journal of Zoology, 79:1794-1800.

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Cautious Around the Trails

Leo Tolstoy once stated that the most important advice he could give would be to “stop a moment, cease your work, look around you.” It’s doubtful Tolstoy had white-tailed deer in mind when he said this, but surely this advice applies to cervids, especially those living near areas that attract walkers, joggers, and cyclists.

Over the past year, a team of biology students from Mitchell Community College have used trail cameras to monitor deer activity throughout greenway patches in Statesville, NC. These cameras have been used to estimate deer population, but researchers have also used them to compare deer activity in different areas. Two groups of cameras were used. Cameras in group A were placed deep in the woods away from human-made recreational trails and group B cameras were placed less than 25 m from the actual greenway trails. The researchers were interested in knowing if deer activity differs as the deer get closer to human used trails. During a 3 month period in the fall 2016, the cameras collected 139 pictures of deer on trails or less than 25 m from the trails and 522 pictures of deer in the deep forest. The pictures were then analyzed. Figure 1 shows the results.

Figure 1. Trail Activity vs. Forest Activity

Figure 1. Trail Activity vs. Forest Activity

 

Deer activity around trails peaks around 8:00 a.m., then drops off significantly. Activity is pretty much nonexistent around trails from 10:00 a.m. to 5:00 p.m. The deer don’t start using the trails again until after 6:00 p.m. On the other hand, deer activity in the deep woods peaks close to 9:00 a.m. and does not hit a low point until 11:00 a.m. During the day, deer activity in the deep woods stays consistently higher than activity along trails. White-tails tend to rest during the day in areas of highly dense vegetation. However, they are not resting for long periods of time. They are alternating between moving, eating, and resting. Our data suggests that this cycle occurs in the deep woods during the daytime hours. Is it simply because that’s where the vegetation is or do human-made trails have something to do with it?

Notice that right around 8:00 p.m., deer activity along the trails becomes higher than activity in the deep woods. It stays like this the entire night. There may be some simple explanations. It could be that the trails provide easier travel for the deer during the night. Maybe the deer are avoiding coyotes, especially when they have fawns to protect. The trails could also provide the deer easier access to the corn and bean fields nearby. Finally, maybe the deer know when people will not be out on the trails, and they purposely chose those times. Is it possible that the presence of people is what actually impacts the deer behavior on a daily basis?

While there is really no way to answer these questions from our small data set, there have been other studies over longer periods of time with more cameras that have looked at some of the same questions regarding this behavior.

Lashley et al. (2014) showed that female white-tailed deer, at baited sites, were 46% more vigilant when fawns were present. They also showed that does and bucks spent more time feeding as the size of the group increased, implying that there is safety in numbers for deer.

Parsons et al. (2016) found that prey species like deer avoided potential predators like dogs, humans, and coyotes in time, but not in space. The deer in this study did not greatly increase vigilance. The researchers concluded that dogs that are on the recreational trails with their human owners have a lesser impact on prey vigilance than free-ranging dogs.

More related to our study, Schuttler et al. (2016) analyzed the head posture of deer in over 3400 pictures to determine if deer are more vigilant in areas with both high human hunting and high coyote activity. What they found was not what they expected. They found that deer vigilance was actually lower in areas with high human recreation. This result is interesting because it may indicate that deer become habituated to human presence in areas such as our greenway spaces.

More than likely, there are a combination of factors that cause deer at this greenway patch to use the trails more during the overnight hours. In the future, more cameras will be used over a longer period of time to attempt to understand how these urban deer stay safe.

 

Not Playing by the “Rules”

Red fox (Vulpes vulpes)

Red fox (Vulpes vulpes)

Legend tells of a fox as black as night, so that it can never be seen in a man’s shadow. Although sometimes seen in juveniles, this black-phase phenomenon is quite rare. Foxes love urban green patches where they can hunt and also enjoy a life of secrecy. Remarkably, in ecosystems with larger predators, they continue to have success.

Regarding this color morph, we must ask several questions:

1) Physiologically, how does this happen?

2) Is this the product of natural selection?

3) If so, what is the evolutionary advantage?

There does not seem to be any specific studies that have looked at this condition in red foxes. However, there are two that look at the genetics of melanism in cats and wolves.

This article looks into the melanistic variants of the Felidae family. The researchers studied the genetic basis, evolutionary history, and adaptive significance of this dark color.

Interestingly enough, the researchers in this article show that traits that are selected in domestic dogs can influence fur color in wild wolves and coyotes.

In the meantime, be on the lookout for this guy in Statesville.

Follow the Crowd and Keep Chewing

The story says that in 1832 a scientist found a deer tooth in a Virginia cave. After close examination, he noticed that the tooth was hollow. That simple observation allowed the scientist to name this animal Odocoileus virginianus. Odocoileus comes from a combination of the Greek words for “tooth” (odontis) and “hollow” (koilos).

Up Close

Up Close

White-tailed deer are distributed throughout eastern North America. It’s these “hollow” teeth that chew up vegetation as they spend a lot of time browsing, which can become extremely heavy in some areas. Their niche, or role, in the ecosystem is replaced by mule deer or blacktail deer in the west. These deer occupy a wide range of habitats, but the main ecological drivers are food and cover.

In North Carolina, white-tails have very little population pressures, and therefore, multiplying is not a problem. Based on 2015 harvest numbers, it is estimated that there are 30-44 deer per 640 acres (1 square mile) in Iredell county. According to the U.S. Forest Service, a deer density of 15 to 28 deer per 640 acres is ideal for forest regeneration. Anything less than 10 deer per 640 acres would cause an overgrown understory. Anything higher than this ideal range would be detrimental for the vegetation. Iredell county falls on the high end.

We are interested in how deer in Iredell county are using city greenway spaces and the adjoining land. For the past three fall semesters, our lab group at Mitchell Community College has utilized trail cameras to estimate white-tailed deer population size at one of these urban greenway spaces. This particular space and the immediate land surrounding it total 657 acres. We used this area as our study site. We set up and deployed cameras from September through November during 2014, 2015, and 2016 using the methods put forth by Texas Parks and Wildlife. As part of these methods, the students set up cameras along transects a specified distance apart. At the end of each camera-trapping period, researchers tallied the total number of doe pictures, fawn pictures, and buck pictures. The researchers also determined how many individual bucks were caught on camera. Sample data for 2016 look like the following:

Total # of deer photographed = 742
     Bucks = 112 (Individual bucks = 8)
     Does   = 668
     Fawns = 32 

Students then used the individual bucks identified (8) and divided by the total number of bucks caught (112) to determine the population estimate multiplier.

Population estimate multiplier = 8 bucks/112 total buck pictures = 0.07

The deer population is estimated using this multiplier.

Bucks =                         8
Does =  668 x 0.07 =  2.24
Fawns = 32 x 0.07 =  46.76
_____________________
Total deer =                57

The student researchers used this exact method for the same study site all three years.

Figure 1. White-tailed Deer Data, 2014-2016

Figure 1. White-tailed Deer Data, 2014-2016

The data from 2014-2016 is shown in Figure 1. We realize that there can be fluctuation in deer numbers from year to year since deer are constantly moving in search of food and cover. Our study site is almost completely surrounded by major roads and/or developed neighborhoods. If 28 deer per 640 acres is ideal, that amounts to 22.9 acres per deer. Figure 1 shows that in 2016, there were 11.5 acres per deer at our site. That represents a very dense population.

Why are these numbers much higher than ideal deer population numbers? Why is the deer density in this space more than the average density in Iredell country? The data could indicate that deer density is greater in areas surrounded by urban development simply because the deer are squeezed into these spaces. There isn’t much food or cover available on interstates on in neighborhoods. The density could also be high at this particular site because nearby residents feed the deer. That would certainly seem to attract more individuals. The next question we wanted to answer was, “How does a higher than ideal deer density impact deer behavior and activity?” Are they active and feeding when deer are suppose to feed (like the books suggest) or do they feed for longer periods of time? What does this mean for understory vegetation.

Figure 3. Deer Activity Patterns

Figure 2. Deer Activity Patterns

Figure 2 shows deer density plotted over time (24 hr). Out of this sample of 471 pictures, deer activity drops off sharply before mid-day, or 12 p.m. The data indicate that the deer in this space are most active around sunrise and sunset, which is typical for this particular species. According to Figure 2, the higher density has not caused the individual deer to change the times in which they are active. However, the deer in this area are putting a tremendous amount of pressure on the vegetation. Simply put, they are eating plants faster than the plants can grow. Walk through just about any patch of forests in the county, and you will notice this.  This may, in fact, have negative impacts not just on vegetation but also those species that rely on that vegetation. In future years, students will collect and analyze data from vegetation plots to quantify vegetation loss and again better understanding of how these deer are impacting this ecosystem.

Foraging or Hiding?

Foraging or Hiding?

White-tailed deer look like they are here to stay in large numbers as they crowd into developed areas. Deer management policies and practices have yet to be successful. Hunting has not been able to put a dent into the population. The deer have no real predators (coyotes don’t really count). Maybe its time to reintroduce a large feline carnivore to North Carolina.

NewsBits 05- Rare sand creatures, Thylacines, and killer cats

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Arabian sand cats, Felis margarita harrisoni, were seen by camera traps for the first time in ten years. One of six subspecies, this cat lives in desert environments. Beyond that, not much is known. Check out the article.

There’s a recent home-made video from South Australia that claims to show a Tasmanian tiger, or thylacine, alive and well. The only thing is is that these creatures were declared extinct in 1936. They were hunted to extinction, but it seems their genetic diversity was limited before they went extinct.

According to a recent study, that looked at the overall impact of invasive predators, found that feral cats have contributed to over 60 extinctions and threaten the most species overall (430). Check it out, and then keep your cat(s) inside.

On the other side of the spectrum, a group of researchers looked at the socioeconomic benefits of re-introducing cougars into the Eastern U.S. The models predict that if cougars successfully recolonize the area, then over 30 years, deer density and deer vehicle-collisions would be reduced by 22%. The total avoided costs in North Carolina alone over 30 years would be just over $30 million, according to the models.

Here’s a fascinating story about Peter and Rosemary Grant and their quest to find evolution in action. The Grant’s are well-known for studying finches in the Galapagos. After decades of studying these birds, they are now focused on looking for the genetic factors driving the adaptations.

We can all agree that there is little downside to taking a walk outside. There may even be benefits.

Want to learn more about the CRISPR-Cas9 technology? Here’s a nice introduction of how it works, and this article explains how it could be used in conservation.