White-tailed deer
White-tailed deer (Odocoileus virginianus) and coyotes (Canis latrans) have both been previously observed in the Fred Stanback Jr. Ecological Preserve, but research relating to predation in the area is lacking. The purpose of this research was to examine whether the white-tailed deer (Odocoileus virginianus) feared predation by coyotes (Canis latrans) in the preserve or not. Four game cameras, checked once a week and directed towards or near an O. virginianus carcass that was set out off-trail in the Fred Stanback Jr. Ecological Preserve, were used to collect images for analysis of temporal occupancy use data. A sudden disappearance of O. virginianus when C. latrans individuals appear seemed to indicate that O. virginianus in the preserve fear predation by C. latrans in some way. Most importantly, O. virginianus might actively avoid C. latrans if fawns or yearlings are present, as young O. virginianus are far more vulnerable to predation.
Keywords: Odocoileus virginianus, Canis latrans, temporal occupancy use, predation threat, fawns, survival
Temporal Occupancy Use by Mesopredators and Prey in the Fred Stanback Jr. Ecological Preserve
White-tailed deer (Odocoileus virginianus) are one of the most common and widespread deer in North America, inhabiting, with the exception of a few western states, most of the United States as well as southern Canada (Dewey, 2003). At night, O. virginianus tend to prefer open areas, but this is not the always the case, as it also depends upon the presence of fawns, as well as the amount of moonlight found at the time (Brown et al., 2011). Within the Fred Stanback Jr. Ecological Preserve in Salisbury, North Carolina, O. virginianus are plentiful and a large number have been captured on game cameras in recent years, both during the day and at night. Fawns have also been observed within the preserve within the past year, both on camera and by eyewitnesses out walking in the preserve or participating in class labs.
Coyotes (Canis latrans) are less common within the preserve, although groups of up to six individuals have been reported in the past by students in the area. As mesopredators, C. latrans are below apex predators in the food chain (Roemer, Gompper, & Van Valkenburgh, 2009). Mesopredators, due to their smaller sizes, are able to thrive in a wide variety of habitats, and are often considered agricultural pests as they tend to be the predators that prey upon smaller livestock on farms (Roemer et al., 2009). However, partly due to the extirpation or near-extirpation of the native red wolves (Canis rufus), mountain lions (Puma concolor), and other apex predators, C. latrans have begun spreading to the East Coast, much farther east than the historic range, and are beginning to replace the apex predators. Out of the original native predators, the loss of C. rufus seems to have had the most noticeable effect on the spread of coyotes (Kilgo, Ray, Ruth, & Miller, 2010). “Mesopredator release” accounts for this, and makes note of the fact that apex predators in some areas no longer suppress mesopredator populations, allowing for species such as C. latrans to spread further than the species would have historically (Ritchie & Johnson, 2009). As a result, there is a more common threat to O. virginianus individuals from C. latrans individuals than there would have been in the past because C. latrans has become increasingly common within the eastern states (Kilgo et al., 2010). This information is especially applicable to the studying of the potential loss of O. virginianus fawns and yearlings in the areas that C. latrans has become more common in due to the information previously mentioned, such as spreading populations.
For O. virginianus fawns, predation by C. latrans in general has shown to be a leading cause of death, even in the Carolinas (Kilgo, Ray, Vukovich, Goode, & Ruth, 2012). Unless an individual is severely ill or weak in general, adult O. virginianus tend to be agile enough to avoid coyotes if a threat is present at all, although there have been cases where O. virginianus individuals were ambushed after they had bedded down and were more vulnerable to an attack (Patterson & Messier, 2003). However, due to the smaller size of O. virginianus fawns and yearlings, there may be more of a risk when C. latrans are present, especially if areas of heavy brush are not accessible to O. virginianus (Kilgo et al., 2010). For example, fawns weigh between 1.5 and 2.5 kg at birth, and are left alone and camouflaged in the brush on the forest floor for up to four hours while the doe forages on her own (Dewey, 2003). As a result, young fawns are far more likely to be found by wandering C. latrans, which have been found to frequently prey upon fawns and younger yearlings at certain times of the year since the younger animals are far easier prey for C. latrans than adult O. virginanus. Other data has been gathered and analyzed in the past in South Carolina that suggests that predation by C. latrans can potentially reduce the O. virginianus population due to the loss of younger O. virginianus, which can be beneficial or detrimental to the O. virginianus population depending on the circumstances (Kilgo et al., 2010).
This carries into studies within the Fred Stanback Jr. Ecological Preserve as well, since the opportunity is available to study the interactions between O. virginianus and C. latrans on a smaller scale where fawns and yearlings are present in addition to many adults. This is where the analysis of temporal occupancy use data can be beneficial in determining whether or not O. virginianus in the ecological preserve fear predation by C. latrans in the area. For example, if there is little to no overlap in times and dates where O. virginianus and C. latrans are seen, there may be an indication of predator avoidance due to O. virginianus considering C. latrans to be a legitimate threat. This experiment could potentially apply to other mesopredators and prey animals in a number of different environments, particularly in areas where mesopredators are beginning to replace the apex predators in the food chain now that many of the apex predators have been extirpated from some areas. This could be applicable both nationally and internationally for a wide range of mesopredators.
Methods
For this analysis, thousands of images were collected using four game cameras, three of which were directed towards a mostly intact O. virginianus carcass. The fourth game camera was placed in the vicinity of the carcass, on a tree facing directly away from it in the direction of the nearest trail, which can be seen in many of the images. The carcass was placed off-trail in the Fred Stanback Jr. Ecological Preserve at Catawba College in Salisbury, North Carolina. The four cameras were checked once a week for roughly two months, and the images were examined for overlapping occurrences of O. virginianus as well as occurrences of C. latrans. For most checks of the game cameras, a laptop was taken in order to immediately transfer pictures then put the memory cards back in to avoid any unnecessary gaps in the data to be continually gathered. The cameras were first set up and left running well in advance of setting out the carcass to continue to gather data of O. virginianus movement within the preserve at specific times. The carcass was left completely exposed to the elements, including rain and several days’ worth of snow which further wore away at the O. virginianus carcass before C. latrans appeared towards the end of the research period to scavenge the remainders of the carcass left behind by vultures, opossums, foxes, and raccoons.
Results
Roughly two months’ worth of temporal occupancy use data was collected in the form of game camera images. Figure 3 depicts the times and dates that either O. virginianus or C. latrans were present on camera. In between sightings of O. virginianus and C. latrans, vultures were present fairly consistently, appearing on three of the game cameras nearly every day that the O. virginianus carcass was left out, and then once in the same spot after the carcass was moved. Most O. virginianus appeared on camera between 2:00 AM and 11:00 AM (Figure 3). No C. latrans individuals were captured on camera until April 1st. Does with fawns were more common earlier in the timeline, while does with older fawns or yearlings were more common later. Notably, does with younger fawns stopped appearing on camera after 11:19 AM on March 21st, while does with older fawns or yearlings appeared on camera until two days later between 8:44 AM and 8:46 AM. There is a nine-day gap between O. virginianus being spotted (a doe with older fawns or yearlings) on March 23rd and two large does appearing on March 31st between 4:07 AM and 4:09 AM before moving on.
After these occurrences, O. virginianus did not reappear on the game cameras until after two solitary C. latrans, appearing to be a male and a smaller female, were captured on camera on April 1st. The first C. latrans appeared on camera at 3:39 AM that morning, while the second C. latrans appeared slightly later and investigated the carcass before eventually dragging it away from the initial site around 5:00 AM and depositing it further off into thick brush. Thorns and vines made it somewhat difficult to track the carcass down at first, potentially meaning the coyotes were aware of the cameras and uncomfortable with the unfamiliar objects to the point where they wanted to relocate the food source to somewhere “safer.” In general, C. latrans also spent a longer amount of time at the carcass site during the usual times that O. virginianus were seen beforehand.
A single O. virginianus was seen on the cameras on April 3rd, at 8:36 AM , two days after C. latrans was last seen on camera, and was only seen on camera for about a minute, although it could have been just off camera in another section of the surrounding woods not covered by the game cameras. In this instance, the O. virginianus individual caught on the images from the cameras was a lone buck, and no does, fawns, or yearlings were seen in the area between the buck and the camera data being collected later. The most common timeframe, with a few exceptions, to find deer on the game camera images was between 1:30 AM and about 11:30 AM. C. latrans appeared within in this timeframe as well. Table 1 also provides this information as well as clear start times and end times for both O. virginianus and C. latrans.
During the time the game cameras were in use, an estimated twenty-four O. virginianus does appeared in total, as did three fawns, eight older fawns or yearlings, and two fully-grown bucks (Figure 1). Although difficult to distinguish individually, some groups, particularly does with their young, seemed to stay close together consistently and reappear on camera in the same groups repeatedly. Does with fawns of any age or with yearlings accounted for approximately 50% of the O. virginianus sightings, while small groups of adult does or lone does accounted for 37.5% of recorded sightings. Lone O. virginianus bucks accounted for the remaining 12.5% of sightings on the game cameras.
There were six recorded instances of does without fawns or yearlings appearing on camera and eight other recorded instances of does with fawns of any age or does with yearlings (Figure 2). The higher percentage of does with fawns of any age or yearlings appears to be particularly important to the study, since the presence of more vulnerable O. virginianus individuals changed in an apparent sequence before the first appearance of C. latrans, with younger fawns disappearing first, followed by the older fawns and yearlings at a later date when the last young O. virginianus appeared.
Discussion
Overall, while more data will be needed to confirm any conclusions in the long term, the current data gathered seems to indicate that adult O. virginianus do not necessarily fear predation by C. latrans; however, when fawns or yearlings are present and C. latrans nears the area, all O.virginianus with young seem to disappear from the area, presumably to attempt to keep their vulnerable offspring from falling prey to C. latrans. The O. virginianus with younger offspring within the preserve avoid the area for several days before and after C. latrans passes through.
Although commonly found in North Carolina today, C. latrans generally remain traditional mesopredators. The species does not seem to have fully replaced the C. rufus or other apex predators that were once found in the state, as adult O. virginianus alone do not appear to fear C. latrans (Schuttler et al., 2017). However, as the population of C. latrans increases and spreads further, this might begin to change as more individuals are around to prey upon O. virginianus.
This points to adult O. virginianus originally rarely being preyed upon by C. latrans, although there have been recorded instances of coyotes preying on adult deer in certain circumstances, where coyotes will attack adult O. virginianus and bite the throat to bring down the individual, usually a sick or weak O. virginianus (Simons, 1988). In general, though, adult O. virginianus have shown to be more than capable of detecting C. latrans in the area and will practice avoidance to stay away from C. latrans, thus avoiding the threat before it can get too close (Lingle & Wilson, 2001). O. virginianus will engage in a number of other antipredator tactics if C. latrans is encountered, but avoidance is by far one of the most common tactics as it is one of the most effective for the survival or safety of both adult O. virginianus in addition to fawns or yearlings (Lingle & Pellis, 2002).
O. virginianus fawns are far more vulnerable to predation by C. latrans, and as a result require thick forest and underbrush to remain safe from the C. latrans threat when C. latrans is present (Turner et al., 2011). The availability of thick underbrush and forested areas is particularly important for younger fawns, since they are often left hidden for hours at a time while the O. virginianus doe browses elsewhere (Dewey, 2003). Given this information, the disappearance of fawns and yearlings from the preserve, which is lacking in the right cover in some areas, just before C. latrans appeared on the game cameras supports this conclusion that O. virginianus at least views C. latrans as a threat to fawns and yearlings since they are smaller, more vulnerable, and have less overall experience dealing with mesopredators the size of C. latrans.
As it stands, more data is needed to draw further conclusions about predation threat, C. latrans, and O. virginianus, which can be gained through a couple more months of monitoring game cameras if another carcass can be acquired for the study. Using the recently acquired data from this most recent study, however, it appears probable that, within the Fred Stanback Jr. Ecological Preserve in Salisbury, NC, fawns and yearlings are most likely the only O. virginianus potentially threatened by predation since they are smaller and more vulnerable. There also appear to be too few coyotes in the preserve to be much of a threat to adult O. virginianus. However, after this particular study was completed, three more C. latrans were reportedly seen in the Fred Stanback Jr. Ecological Preserve by Catawba College students. As a result, additional data on C. latrans must be collected in the future via game camera usage, predator-attracting carcasses, and tracking techniques to further verify the potentially-growing population of C. latrans in the ecological preserve.
