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2011 SOUTHEASTERN NATURALIST 10(4):731–740
Food Habits of Red Wolves During Pup-Rearing Season
Justin A. Dellinger1,*, Brian L. Ortman1,Todd D. Steury2, Justin Bohling3,
and Lisette P. Waits3
Abstract - Canis rufus (Red Wolf) is critically endangered, with the only wild population
consisting of <150 individuals. Currently, little is known about the food habits of
this population. Such information may be vital to managing for the population’s longterm
persistence. We collected scats of Red Wolves for two consecutive pup-rearing
seasons from six packs, classified contents into prey categories, and assessed diet composition
for each pack. Five of the six packs studied consumed only mammalian prey
items. Adult Odocoileus virginianus (White-tailed Deer) and White-tailed Deer fawns
accounted for 37–66% of diet of Red Wolves depending on the metric of diet composition.
Adult White-tailed Deer and White-tailed Deer fawns accounted for 21–83% of
the diet of individual packs of Red Wolves according to biomass consumed. Two packs
regularly consumed foods associated with humans. Generalized linear modeling indicated
that diet varied between packs and was not influenced by reproductive status, nor
did diet vary between years.
Understanding diet of endangered species is necessary for proper management
of such species and to determine suitable habitats in which to re-introduce
individuals of an endangered species. Prior to the re-introduction of Canis rufus
Audubon and Bachman (Red Wolf) into part of their native range in 1987, no
large carnivore had been successfully re-introduced (Phillips et al. 2003). For >20
years the re-introduced population of Red Wolves has survived and reproduced in
a habitat matrix altered by humans. A better understanding of what Red Wolves
consume in a human-altered landscape is useful to future re-introductions.
Basic ecological research on Red Wolves in the wild prior to recovery efforts
was limited due to their small population and difficulty in differentiating adults
and juveniles from hybrids and Canis latrans Say (Coyote) (Phillips et al. 2003).
After re-introduction, most research concerning Red Wolves has dealt with resolving
the identity of the species and distinguishing hybrids from Red Wolves
using various genetic techniques (Adams et al. 2007, Miller et al. 2003). Thus,
information on the basic ecology of Red Wolves, although vital to recovery and
management, is lacking.
Although few studies have examined food habits of Red Wolves, they are
considered generalists and opportunistic like most canids (Mech 1970, Paradiso
and Nowak 1972). Studies on remnant Red Wolf populations in Texas and
Louisiana concluded that small mammals constituted a large part of the species’
1Department of Biological Sciences, 331 Funchess Hall, Auburn University, AL 36849.
2School of Forestry and Wildlife Sciences, Auburn University, AL 36849. 3Department of
Fish and Wildlife Resources, University of Idaho, College of Natural Resources, PO Box
441136, Moscow, ID 83844-1136. *Corresponding author - firstname.lastname@example.org.
732 Southeastern Naturalist Vol. 10, No. 4
diet (Paradiso and Nowak 1972, Shaw 1975). Only Shaw (1975) documented
Red Wolves preying on species larger than Procyon lotor L. (Raccoon); however,
only 19 scats were collected for that study. Following re-introduction of
Red Wolves to a part of their historic range in 1987, Red Wolves were observed
to prey upon Odocoileus virginianus Zimmermann (White-tailed Deer) and
Raccoons on barrier islands and on the Albemarle Peninsula in North Carolina
(Phillips et al. 1995, 2003). Red Wolves also preyed on Sus scrofa L. (Wild
Boar) in Great Smoky Mountains National Park (Phillips et al. 2003). Although
previous studies have provided insights into the diet of Red Wolves, no study
has assessed variation in diet of packs of Red Wolves, with the exception of
Phillips et al. (1995), which compared diets of two packs, one of which no longer
exists (Rabon 2010).
Our objective was to determine food habits of Red Wolves. Our specific goals
were to determine overall diet of Red Wolves during the pup-rearing season,
examine variation in diet among packs and between years, and determine if pups
influence the diet of Red Wolf packs.
This study occurred within the Red Wolf Recovery Experimental Population
Area (RWREPA) on the Albemarle Peninsula in northeastern North Carolina.
At the time of this study, the area was home to the only wild population of
Red Wolves in the world. The study area consisted of >6650 km2 of federal,
state, and private lands in five counties (Beaufort, Dare, Hyde, Tyrrell, and
Washington). Federal lands within the study area included Alligator River National
Wildlife Refuge, Pocosin Lakes National Wildlife Refuge, Swan Quarter
National Wildlife Refuge, Mattamuskeet National Wildlife Refuge, and a bombing
range shared by the United States Navy and Air Force. State lands included
numerous game management properties, while private lands were primarily
timber plantations and agricultural fields. The study focused on packs in Tyrrell
and Dare counties (Fig. 1).
Major land-cover types in the study area were agricultural fields (30%);
commercial pine (Pinus spp.) plantations (15%); Pocosin (15%; Pinus serotina
Michx. [Pocosin Pine] and Persea palustris (Raf.) Sarg. [Swamp Bay]); nonriverine
swamp forests (10%; Nyssa spp.[tupelo], Liquidambar styraciflua L.
[Sweetgum], Acer rubrum L. [Red Maple], and Chamaecyparis thyoides (L.)
B.S.P. [Atlantic White Cedar]); and saltwater marsh or open water (10%). Minor
land-cover types comprised the remaining area (20%). Climate was characterized
by four full seasons of nearly equal length with annual precipitation averaging
127 cm. Temperatures averaged 5 °C in winter and 27 °C in summer. Elevation
ranged from sea level to 50 m (Beck et al. 2009). Potential prey species included
White-tailed Deer, Sylvilagus floridanus Allen (Eastern Cottontail), Sylvilagus
palustris Bachman (Marsh Rabbit), Raccoons, Wild Boars, Myocastor coypus
Molina (Nutria), Ondatra zibethicus L. (Muskrat), Sigmodon hispidus Say and
Ord (Hispid Cotton Rat), Mus musculus L. (House Mouse), Oryzomys palustris
Harlan (Marsh Rice Rat), Reithrodontomys humulis Audubon and Bachman
2011 J.A. Dellinger, B.L. Ortman,T.D. Steury, J. Bohling, and L.P. Waits 733
(Eastern Harvest Mouse), Colinus virginianus L. (Northern Bobwhite), and
Meleagris gallopavo L. (Wild Turkey) (Phillips et al. 2003). Co-occurring carnivores
included Urocyon cineroargenteus Schreber (Gray Fox), Vulpes vulpes
L. (Red Fox), Coyotes, Canis lupus familiaris L. (Domestic Dog), Lynx rufus
Schreber (Bobcat), and Ursus americanus Pallas (American Black Bear).
Survey methods and design
Scats were collected during the pup-rearing season, May–July in 2009 and
2010. Because about 75% of the Red Wolves resided on private land, access to
private property played a key role in determining which packs were selected for
study. The territories of the Milltail, Timberlake, Tyson, Columbia, Northern, and
Kilkenny packs (Fig. 1) were surveyed for scats. Paved, gravel, and dirt roads,
and game trails were surveyed on foot within known territories of the packs.
Territorial boundaries were known based on surveys conducted by US Fish and
Wildlife Service biologists (Chris Lucash, USFWS Red Wolf Recovery Program,
Al, Alligator River Wildlife Refuge, Manteo, NC, pers. comm.). In 2009, Milltail
and Tyson packs produced 3 and 4 pups, respectively. In 2010, Milltail, Tyson,
Figure 1. Map of Red Wolf Recovery Experimental Population Area in northeastern
North Carolina and locations of packs of Red Wolves (Canis rufus) studied in 2009 and
2010. Map shows the boundaries of counties, management zones of the Red Wolf Recovery
Experimental Population Area, and federal and commercial lands.
734 Southeastern Naturalist Vol. 10, No. 4
Northern, and Kilkenny packs produced 7, 6, 3, and 4 pups, respectively. Columbia
and Timberlake packs did not produce pups either year (Chris Lucash, pers.
comm.). Each territory was surveyed at least once per week. For our analysis,
the sample unit was the pack: we assumed diet of individuals was representative
of the pack. Rarefaction curves were constructed to determine the relationship
between number of scats collected for a given pack in a year and the number of
prey items detected to assess if sample sizes were adequate.
Identification of scats
During the 2009 field season, a sample of fecal matter was taken from all
scats and placed in individual 2-ml vials containing 1.4 ml DET buffer solution
(Frantzen et al. 1998) to preserve DNA. The remainder of each scat was placed
in a plastic bag and stored below 0 °C until DNA analyses were completed. Fecal
DNA was identified to species and then individual following the methods
of Adams (2006) and Adams et al. (2007). For a scat to be identified as Red
Wolf or Coyote using fecal DNA genotyping, it also had to be identified to individual
animals. Genotypes obtained from scats were compared to genotypes
of known Red Wolves and Coyotes in the area to match scats to known individuals.
Since our sample unit was the pack, scats from unknown individuals
were discarded. Scats determined to be from known Red Wolves from the target
packs were analyzed for prey contents.
Ninety-six percent of scats collected in 2009 and identified as Red Wolf
matched genotypes of individuals from packs of interest. Thus, we decided it
was unnecessary for Red Wolf scats to be related to individuals since most scats
collected within territories of packs of interest and identified as Red Wolf could
be attributed to an individual of that pack. Because our sample unit was the pack,
we only identified scats collected in 2010 to species using more cost efficient
techniques. Diameters of scats were measured upon collection for both field
seasons. After generating a normal-distribution probability function for scats collected
in 2009 and identified via faecal genotyping, it was determined that canid
scats ≥29 mm in diameter had <5% probability of having been deposited by a
Coyote (Dellinger 2011). Therefore, any canid scats collected in 2010 ≥29 mm
in diameter were labeled Red Wolf. Scats collected in 2010 <29 mm in diameter
were identified using scat dogs (Long et al. 2007). The scats dogs were not used
to find scats; rather they were used to distinguish Red Wolf scats collected in
2010 from co-occurring carnivores. The scat dogs were trained using scats collected
directly from captured wild Red Wolves and co-occurring carnivores (e.g.,
Coyotes, Bobcats, and Domestic Dogs), as well as scats collected in 2009 and
identified as Red Wolf or Coyote. The scat-detection dog was 96% accurate in
training trials at distinguishing scats of Red Wolves from co-occurring carnivores
(Dellinger 2011). Thus, we deemed the scat-detection dog was accurate and able
to identify Red Wolf scats collected during the 2010 field season.
Identification of prey items and descriptive analysis of diet
Scats identified as Red Wolf were examined for content. Scat contents (e.g.,
hair, skulls, and teeth) were identified by comparison to reference materials.
2011 J.A. Dellinger, B.L. Ortman,T.D. Steury, J. Bohling, and L.P. Waits 735
Prey items in scats were designated as belonging to one of nine prey categories:
adult White-tailed Deer, White-tailed Deer fawns, small rodents (Hispid Cotton
Rat, Marsh Rice Rat, Eastern Harvest Mouse, and House Mouse), large rodents
(Nutria and Muskrat), rabbits (Marsh Rabbits and Eastern Cottontails), Raccoons,
Wild Boars (feral and domestic), anthropogenic material, and other (prey
items not occurring frequently enough to justify a unique category, e.g., grounddwelling
birds and terrestrial invertebrates).
We used four metrics to rank and determine percent contribution of prey items
in scats: percent frequency of occurrence, relative volume of remains, relative
weight of remains (Ciucci et al. 1996), and biomass ingested (only for mammalian
prey items) calculated using the regression equation of Floyd et al. (1978).
Various methods for describing diet were used because each is recognized as
having biases and comparing them gives a better description of diet than any
single method (Ciucci et al. 1996). Items that were <1% of a scat were ignored
(Ciucci et al. 1996). We excluded prey categorized as other from biomass rankings
because not all prey species included in this category were mammals (Floyd
et al. 1978). Prey category anthropogenic material was only included for percent
frequency of occurrence because digestibility of this prey category was unclear
and likely biased.
Quantitative analysis of diet
To determine which variables best accounted for variation in diet based on
differences in occurrence of prey items in scats, we developed generalized linear
models (GLMs). A global GLM with a Poisson distribution and an offset, to account
for differences in number of scat samples collected, was first constructed by
modeling percent frequency of occurrence of prey items grouped by a four-way
interaction between pack, year, prey item, and reproductive status. We determined
the most parsimonious model using Akaike’s information criterion corrected for
small sample sizes from global model and all possible subsets (AICc; Burnham
and Anderson 2002). We interpreted odds ratios using the link function e(coefficient),
and derived them using coefficient estimates of the most parsimonious model to
determine likelihood of consumption of a given prey item (Manly et al. 2002).
Odds ratios detail likelihood of consumption of one prey item over another for
a given pack as well as the likelihood of one pack consuming a prey item over
another pack consuming the same prey item.
In 2009 and 2010, we collected 176 and 279 Red Wolf scats , respectively.
Rarefaction curves of diet diversity for each pack per year leveled off at 20 scats
regardless of diversity of diet. We found at least 26 scats for each pack per year;
thus, there was a low likelihood that we missed any prey items regularly consumed
by the Red Wolf packs. Therefore, our sample sizes for determining diet
composition of Red Wolf packs were deemed sufficient. We do not suggest 20
scats are sufficient for determining diet of Red Wolves for future studies, rather
736 Southeastern Naturalist Vol. 10, No. 4
future studies should use rarefaction curves in their own analyses to assess the
adequacy of their sampling efforts.
Estimates of biomass consumption indicated adult White-tailed Deer and
White-tailed Deer fawns combined represented 66% of total biomass of prey
consumed. Percent frequency of occurrence, relative volume, and relative weight
of remains indicated adult White-tailed Deer and White-tailed Deer fawns combined
represented 37, 49, and 49%, respectively, of total prey items consumed by
all packs (Fig. 2). Spearman rank correlation coefficients showed strong agreement
between ranks of importance of prey items between metrics both within and
across packs (rs > 0.78).
Based on AICc rankings, the most parsimonious GLM for predicting variation
in diet of Red Wolf packs included prey, pack, and prey by pack interaction.
Year and reproductive status were not significant variables in predicting variation
in diet of Red Wolf packs. The Akaike weight of the most parsimonious
GLM was 0.96. The next best GLM included reproductive status as a variable
and had a ΔAICc = 170 and Akaike weight < 0.01. Since year was not an
important variable in the most parsimonious GLM, diet composition was conducted
with data combined across years for all packs. Given that year was not a
significant variable, we assume the different methods of identification of scats
did not bias our results.
Odds ratios were derived using the link function e(coefficient) and coefficient
estimates of the most parsimonious GLM (Table 1). Three of the six packs (Columbia,
Timberlake, and Northern) were more likely to consume White-tailed
Deer fawns than any other prey item. Milltail, Tyson, and Kilkenny were most
likely to consume small rodents, domestic pig, and large rodents, respectively.
Compared to all other packs, Northern was most likely to consume both Adult
White-tailed Deer and White-tailed Deer fawns.
Table 1. Odds ratios for counts of occurrence in diet of packs of Red Wolves in the Red Wolf
Recovery Experimental Population Area in northeastern North Carolina, 2009–2010. Odds-ratios
were derived from coefficient estimates of most-parsimonious generalized linear model using link
pogenic Deer Large Wild Small
Pack material Adult Fawns rodents Other Boar Rabbit Raccoon rodent
Columbia NCA 1.00B 5.81 0.43 0.14 NC 1.42 0.28 1.28
Milltail 5.26 2.72 1.14 0.71 4.95 NC 0.57 1.84 5.70
Timberlake 0.14 4.01 6.11 1.99 0.14 1.99 3.71 0.28 0.43
Tyson 0.14 0.71 4.14 1.00 0.43 4.55 2.27 2.56 4.14
Northern 0.28 5.99 8.17 2.27 0.85 0.28 5.10 1.02 0.28
Kilkenny NC 0.86 5.81 6.27 NC 0.28 0.79 0.28 2.00
2011 J.A. Dellinger, B.L. Ortman,T.D. Steury, J. Bohling, and L.P. Waits 737
Figure 2. Percentage composition of diet of packs of Red Wolves (Canis rufus) according
to each metric of diet composition. All percentages for each pack per metric sum to 100.
Percentages are given for years combined. Percent frequency of occurrence, relative volume
of remains, relative weight of remains, and estimated biomass consumed according
to Floyd et al. (1978).
738 Southeastern Naturalist Vol. 10, No. 4
Our study revealed that Red Wolf packs primarily consumed mammalian prey
species during pup-rearing season. Overall, diets of Red Wolf packs were composed
primarily of adult White-tailed Deer and White-tailed Deer fawns during
pup-rearing season (Table 1, Fig. 2). Consumption of large-sized mammals such
as these was expected given the size of adult Red Wolves (male Red Wolves average
27.5 kg, females 21.5 kg; Paradiso and Nowak 1972), their tendency to hunt
in packs, and the energetic demands of rearing pups during this time of year. The
only other large-sized wild mammal available to all Red Wolf packs, feral Wild
Boars, was only consumed by Timberlake pack. Phillips et al. (2003) reported
Red Wolf packs hunting and bringing down feral Wild Boars.
Although Red Wolf packs consumed primarily adult White-tailed Deer,
White-tailed Deer fawns, or both during pup-rearing season (Table 1, Fig. 2),
each pack differed from one another in consumption of prey items (Table 1).
It is likely that this prey-by-pack interaction is related to consumption of secondary
or tertiary prey and not primary prey. This could be the result of an
increase in abundance of a given prey within the territory of a pack compared
to territories of adjacent packs or an increase in selection for a given prey by a
particular pack relative to adjacent packs. Variation in diet between groups of
social carnivores could be the result of differential foraging skills and habits
transmitted along kinship lines (Mech 1970). Variation in diet due to differences
in habitat composition of the territories is unlikely given the low diversity of
habitat types across the RWREPA (Beck et al. 2009). Variation in diet of Red
Wolf packs during pup-rearing appears to be primarily related to consumption
of secondary and tertiary prey, not primary prey which was adult White-tailed
Deer and White-tailed Deer fawns. Diets of packs of Red Wolves during puprearing
did not vary between years; however, a longer study is needed to better
assess yearly fluctuations in diets of Red Wolf packs. Diets of Red Wolf packs
were not found to vary with reproductive status. This is possible if Red Wolves
increase consumption of primary prey items rather than increasing the diversity
of prey items consumed.
Consumption of anthropogenic material by the Milltail pack and domestic
Wild Boar by the Tyson pack was not surprising given that territories of these
packs contained an active garbage dump and carcass pit, respectively. Ciucci et
al. (1997) reported a pack of Canis lupus L. (Gray Wolf) in Italy relied almost
entirely on anthropogenic material from garbage dumps and remains of domestic
animals from carcass dump sites. Consumption of human-related foods could
raise concern about the reliance of wild Red Wolves on foods associated with humans,
particularly pets and domesticated animals. Given that these two packs can
catch and consume native prey (Fig. 2), we assume packs of Red Wolves do not
seem to rely heavily on foods associated with humans, but will readily consume
such foods if given the opportunity. Biologists might consider actions to reduce
reliance of these packs on foods associated with humans to reduce potential of
Red Wolf-human interactions. Barlow et al. (2010) suggest that, in the face of
little scientific data, erection of fencing around sources of human derived foods
2011 J.A. Dellinger, B.L. Ortman,T.D. Steury, J. Bohling, and L.P. Waits 739
is generally a good method for reducing reliance of large carnivores on such
sources of food.
Our findings suggest that after >20 years since Red Wolves were first re-released
to the RWREPA, most packs are surviving completely by consuming wild
prey, at least during pup-rearing, within a human-altered landscape. Furthermore,
packs of Red Wolves appear capable of catching and consuming a sufficient
amount of prey to support reproduction. The ability of Red Wolves to catch and
consume natural prey in a human-altered landscape demonstrates their ability to
survive and reproduce in close proximity to humans. Future studies should focus
on diet of Red Wolves during winter or throughout the year and attempt to assess
whether Red Wolves consume prey in proportion to availability or selectively
We thank personnel of the USFWS for their support. C. Lucash, A. Beyer, F. Mauney,
R. Nordsven, M. Morse, D. Rabon, J. Hinton, J. McVey, and C. Proctor for assistance in
conducting field work and obtaining data. Weyerhaeuser Company provided access to its
lands and spatial data. E. Herrera and A. Knapp provided laboratory assistance. Research
was funded by an Auburn University Graduate Research Award. The findings and conclusions
in this article are those of the authors and do not necessarily represent the views of
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