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Facultative scavenging and carrion guild participation by Lynx rufus in the presence of young.

The bobcat is widely distributed from southern Canada to northern Mexico and is present in all of the 48 contiguous states of the united states with the exception of the Ohio River Valley, the southern Great Lakes region, and the northern Mississippi Valley where they have been overhunted and mostly eradicated (Lariviere and Walton, 1997; Brockmeyer and Clark, 2007; Rippley et al., 2012). Bobcats are described as almost exclusively carnivorous, with rabbits and other small rodents such as mice and squirrels dominating their diets (Rolley and Warde, 1985; Thornton et al., 2004; Brockmeyer and Clark, 2007); they generally consume all parts of small- to medium-sized prey and can readily digest the bones of small mammals (Brockmeyer and Clark, 2007).

Carrion scavenging is not considered common behavior in these animals but has been sparsely documented. Adult bobcats were noted to have scavenged on 5% of deer carcasses examined in an Idaho study, compared with 79% of the carcasses which were scavenged by coyotes (Koehler and Hornocker, 1991). Other studies have found large quantities of deer tissue in the stomach contents of harvested bobcats (Brockmeyer and Clark, 2007). While bobcats are capable of catching and consuming larger prey such as deer, only 10% of deer carcasses examined showed signs of being killed by bobcats (Koehler and Hornocker, 1991). It is likely that bobcats, similar to other predators, are in fact opportunistic scavengers, and forage upon the remains of fatally wounded or diseased animals, especially in winter. The low percentage of deer whose death was directly attributable to bobcat predation, when contrasted with the high percentage of deer in stomach contents seasonally in winter supports this reconceptualization of bobcat behavior and their role in the scavenging guild. Further instances of bobcat scavenging include a single case of necrophagus scavenging on a human corpse reported in a forensic cadaver study (Rippley et al., 2012), and a recent note in which the stomach contents of a freshly road-killed bobcat contained a gray squirrel (Sciurus carolinensis) that had to have been consumed as carrion due to the presence of blow fly (Calliphoridae) eggs (Platt et al., 2010).

Herein we report scavenging behavior by a female bobcat and cub at domestic pig (Sus scrofa) carcasses during a carrion utilization study in central Oklahoma. These observations were made during the first of three series of carrion placements focusing on eliciting local scavenger guild dynamics. The research was conducted at the Oklahoma Department of Wildlife Conservation's 226.6-ha Lake Arcadia Conservation Education Area, in north central Oklahoma (35[degrees]37'28"N, 97[degrees]23'25"W). The area is a combination of riverine habitat, mixed grassland prairie, and cross-timbers. The cross-timbers ecoregion covers large areas of central Oklahoma; it is comprised mainly of scrub oak forest interspersed with tall-grass prairie (Disney et al., 2008). This diverse landscape provides habitat for a wide variety of mammalian species including large predators and mesopredators, as well as small omnivores (Disney et al., 2008). Several suburban housing editions are located on the southern edge of the conservation area, with the closest housing to the carcass drop location being 0.54 km to the southeast. The area is open to the public and is frequently used by humans for outdoor recreation, fishing, and bow deer hunting.

Behavioral observations were made from video and still photos. The first visit by the adult bobcat to the carcasses came approximately 28 h after their placement at 2001 h on 31 October 2012. These first visits were brief, 1.5 min and 30 s, respectively. At 2111 h the bobcat returned and spent 46.5 min feeding at the carcass. The duration of feeding episodes increased throughout the observation period. At the last feeding observation, the bobcat fed for 2 h 12 min. Average visit duration was 15.83 min. Average temperature at visits was 10[degrees]C.

Two other species, the coyote (Canis latrans) and the Virginia opossum (Didelphis virginiana), were also identified visiting and feeding on the carcasses. These visits are outlined by species according to experiment day and time (Fig. 1). These visits demonstrate a clear delineation in the time that the scavenger species visited the carcasses. The bobcats were often active during the middle of the day, but maintained an overall pattern similar to those previously documented, with the majority of their activity falling between the hours of 0400-1000 h and 1800-2400 h (Rippley et al., 2012). The Virginia opossums fed heavily between 1900-2400 h, overlapping with bobcats' feeding times. The two species did not share carcass space simultaneously but would access the carcass one after the other (Fig. 1).

[FIGURE 1 OMITTED]

The adult female bobcat fed alone at the first of two carcasses fed on; this carcass was removed from the area by a coyote within two days of placement. The carcass at the time of feeding was mostly fresh with some drying out of exposed tissues and no insect activity. Once this carcass was unavailable, the adult bobcat moved to the second available carcass. The adult female was joined at this time by a juvenile bobcat presumed to be its cub, as bobcats are solitary other than female-offspring groups (Janecka et al., 2006). The cub was also much smaller in size and had less-developed facial tufts. Sex could not be determined. We confirmed visually through markings and size that the same two bobcats, and not multiple other cats, were being observed throughout the experiment.

While the bobcats were in the area of the carcass contemporaneously, they did not always feed simultaneously. The adult often sat nearby while the cub ate. The cub, in turn, investigated and played as the adult ate. However, there were several incidences where the two were caught on camera together. The first confirmation of the adult bobcat being accompanied by a cub occurred at 0700 h on 4 November 2012. From this point on, most of the visits involved both of the bobcats instead of only the adult, which had been feeding alone at the first carcass.

The adult bobcat was observed covering the second carcass with grass and leaves. She was more thorough initially in this endeavor and less so as time went on. The first day that the adult bobcat visited the second carcass, she completely covered it to the extent that it was hardly visible. By the last day the carcass was present it lacked concealment of any kind. The bobcat used dead grass and leaves from the immediate vicinity while it was in the open grass, and used leaves and sticks when the carcass was in a stand of scrub trees, where it was last observed.

The bobcats began feeding at the neck and shoulder region of the carcass. They fed heavily on large muscle groups, stripping the carcass to bone in many places. They were not observed feeding on viscera or integument of the carcasses, or damaging or ingesting any bone. In several instances, the adult female bobcat was observed tearing and pulling at the hide to separate it, exposing skeletal muscle and fat. The bobcats remained in the area and fed on the intact carcass until it was reduced to only skin and bones. A coyote then removed it from the area.

This is the first directly observed participation by the bobcat as part of the carrion recycling guild in this region. Foraging duration and carcass visitation frequency indicates that female bobcats might readily engage in necrophagus foraging behaviors at carrion, especially when caring for young, on a more-regular basis than previously hypothesized.

These observations suggest reframing our assumptions about the species and proffer the notion that they might be better categorized as opportunistic facultative scavengers, similar to other large predator species. Although it is commonly suggested that bobcats prefer fresh kills (Brockmeyer and Clark, 2007), these observations demonstrate willingness to scavenge the remains of large vertebrates when available. The second carcass, which was fed on the most heavily, was exposed for three days before the bobcats began feeding on it. Due to the colder temperatures, the carcass stayed fresh with little insect activity and decomposition. This likely influenced the choice to utilize this resource. It was a relatively fresh, free food energy source, high in fat and protein.

The caloric value of a pig carcass is 472 kcal/100 g; in contrast an average rabbit is only approximately 117 kcal/ 100 g (U.N. Food and Agriculture Organization, http:// www.fao.org). The bobcat itself needs to consume, on average, 138 kcal per/kg per day in all seasons (Lariviere and Walton, 1997). This comparison shows the greater value of the carrion resource. Considering that there is relatively no search time involved in the use of the carrion resource once it has been initially located, as compared to hunting rabbits or mice, the carrion resource is still much more valuable than other available resources, even if live prey resources of the bobcat may be present. While swine is not a typical food source of bobcats, this new food energy source might not be rejected in lieu of typical prey due to its low handling and searching time compared to high energetic payout. This would also explain the observation of a bobcat feeding on a human cadaver, another atypical resource (Rippley et al., 2012). This hypothesis is further supported by recent data on foraging behaviors of bobcats in the Chihuahuan Desert. An analysis of prey species selection revealed that bobcats acted as specialized foragers, whose prey selection was not based on available density. Lagomorphs had the highest probability of selection despite lower availability (Lopez-Vidal et al., 2014). The bobcats were seeking out energetically more-valuable prey rather than whatever happened by.

The home range of a female bobcat can be from 11 to 15 [km.sup.2] in Oklahoma (Rolley, 1985; Lariviere and Walton, 1997). However, it is likely that the home range of this particular bobcat female is less than that distance due to the nature of the fragmented suburban area around the wildlife management area. The preserve itself is relatively small at only 2.26 [km.sup.2] and is surrounded by suburban housing. There is evidence that bobcat populations decrease with proximity and intensity of urbanization and that they are less willing to cross roads and developed areas than are other predators such as coyotes (Ordebana et al., 2010; Poessel et al., 2014). The viable area of use might be smaller here than for other bobcat habitats and potentially contributed to these particular bobcats scavenging as heavily as they did. There is also the probability that the smaller area has less available hunting resources, pushing the felids to use resources they might not use under other conditions. We hypothesize that this scavenging behavior pattern might become more prevalent in bobcats in fragmented habitats such as this one, but more research is needed.

While bobcats are considered to be atypical scavengers, they, like many other predators, will partake heavily in facultative necrophagus or opportunistic scavenging under the right circumstances. In this case, those circumstances are considered to be underpinned primarily by the presence of young. The domestic pig carcasses were a high-yield, opportunistic, free resource that were readily taken advantage of, likely due to the high fat content and fresh condition. This study suggests bobcats will take advantage, similar to other predators, of opportunistic carrion in specific conditions. The presence of the cub is seen as one of, if not the primary driver(s) in the necrophagus scavenging behavior observed in this study. Had the adult not had the added resource burden of providing for the still-dependent offspring, as well as herself, this scavenging event might not have occurred. This is further supported by the fact that scavenging by bobcats was not observed in either of the other two experiments, nor were any male bobcats observed scavenging. It has been suggested in previous research that scavenging increases in the breeding season in other species due to increased energetic needs (O'Brien et al., 2010). It is likely that this increase is maintained once offspring arrive, as was evidenced here. Further research is needed in order to understand just how prolific scavenging is among bobcats and if it is truly related to offspring dependency.

We thank the Oklahoma Department of Wildlife Conservation for access to the management area to conduct this research, especially officer D. Griffith and aquatic education coordinator D. Springer. This research was financially supported by the Office of Research and Grants at the University of Central Oklahoma, the W. Roger Webb Forensic Science Institute at the University of Central Oklahoma, and the Forensic Science Foundation Jan Bashinski grant. We thank N. Nieves for the Spanish resumen. We would also like to thank W. Caire for his assistance in the preparation of this manuscript.

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Submitted 4 February 2015.

Acceptance recommended by Associate Editor, Troy Ladine, 8 July 2015.

KAMA A. KING, * WAYNE D. LORD, HEATHER R. KETCHUM, AND R. CHRISTOPHER O'BRIEN

W. Roger Webb Forensic Science Institute, University of Central Oklahoma, Edmond, OK 73034 (KAK, WDL)

Department of Biology, University of Central Oklahoma, Edmond, OK 73034 (WDL)

Department of Biology, University of Oklahoma, Norman, OK 73019 (HRK)

Henry C. Lee College of Criminal Justice and Forensic Science, University of New Haven, New Haven, CT 06516 (RCO)

* Correspondent: kking51@uco.edu
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Title Annotation:Notes
Author:King, Kama A.; Lord, Wayne D.; Ketchum, Heather R.; O'Brien, R. Christopher
Publication:Southwestern Naturalist
Article Type:Report
Date:Dec 1, 2015
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