THESOUTHWESTERN NATURALIST 44(1):83-86 MARCH1999

FOOD PROVISIONING BY ISLAND FOXES, UROCYONLITTORALIS, TO CONSPECIFICS CAUGHT IN TRAPS

DAVID K. GARCELON, GARY W. ROEMER, R. BRAND PHILIPS, AND TIMOTHY J. COONAN

Institute for Wildlife Studies, P.O. Box 1104, Arcata, CA 95518 (DKG, GWR) Department of Fisheries and Wildlife, Utah State University,Logan, UT 84322 (RBP) Channel Islands National Park, 1901 SpinnakerDr, Ventura, CA 93001 (TJC) Present address of GWR:Department of Biology, Universityof California, Los Angeles, CA 90095

ABSTRACT-Preyitems were found outside of welded-wire cage traps containing island fox pups (Urocyon littoralis) on 24 occasions and outside of traps containing adult foxes on 11 occasions. Prey items included mice, lizards, and birds. Island fox pups were observed foraging with adults and were caught with adults in the same trap on 22 occasions. We believe fox pups receive ex- tended parental care and were provisioned while in the traps.

RESUMEN-En 24 ocasiones se encontraron restos de presas afuera de trampasjaulas-de alambre soldado, en cuyo interior habian cachorros de zorros islefios (Urocyon littoralis) atrapados. Asim- ismo, en otras 11 ocasiones se encontraron estos mismos tipos de presas afuera de trampas que contenian zorros adultos atrapados. Los citados restos incluian presas tales como ratones, lagartijas y aves. Los cachorros de zorros islefios han sido observados buscando alimentos junto con los adultos y en 22 ocasiones fueron atrapados juntos en la misma trampa. Creemos que los cachorros reciben cuidado de los padres por un prolongado periodo de tiempo y que los adultos se encargan de alimentar a los cachorros mientras estos permanecen en las trampas.

Prolonged periods of parental dependency est North American canid. During summer, fe- are common in behaviorally advanced carni- males and males on San Clemente Island av- vore species within the Canidae, Felidae, Viver- erage 1.6 kg (SE = 0.24 kg, n = 155) and 1.9 idae, and Hyaenidae (Gittleman, 1989). Many kg (SE = 0.25, n = 146), respectively, and feed of these species carry prey back to the den for primarily on insects, fruits, and small mammals their young, or regurgitate food to their young (Laughrin, 1977; Collins, 1980; Moore and at the den site (Mech, 1970; Moehlman, 1979; Collins 1995). From an energetic standpoint, Hill, 1980; Rasmussen and Tilson, 1984; Hole- rodents, birds, and reptiles may be the only kamp and Smale, 1990). This behavior, also food items that small canids can transport ef- known as provisioning, could have arisen be- fectively back to the den for dependent pups cause lactation is energetically less efficient (Lindstrom, 1994). We report on instances of than the direct transfer of solid food (Hole- presumed attempts to provision island fox kamp and Smale, 1990). Furthermore, levels of pups and adults after their capture in box metabolizable energy can increase to 1.5 to 3.5 traps. times basal levels during peak lactation and may be accompanied by a 20% weight loss (Of- MATERIALS AND METHODS-From 1988 through tedal and Gittleman, 1989). In female carni- 1996 demography of island fox was studied on the vores such severe energetic demands can be California Channel Islands (Roemer et al., 1994). sustained only for a short period. Therefore, Another study conducted on San Clemente Island, involving effects of feral cats (Felis catus) on popu- provisioning of young at a den or rendezvous lations of small mammals and reptiles, occurred site may be necessary until offspring are suffi- from 1992 through 1994 and included numerous ciently developed to escape predators and to captures of island foxes. The study populations in- accompany a single adult or a pack when for- habit San Miguel, San Clemente, and Santa Cruz Is- aging. lands, which are 37 km2, 157 km2, and 249 km2, re- Island foxes (Urocyon littoralis) are the small- spectively. Trapping efforts were conducted on a 84 The Southwestern Naturalist vol. 44, no. 1

10 2.5

8 2.0

6 1.5

Provisioned

4 1.0 Weight(kg)

Percent

2 0.5

0 .0.0 May Jun Jul Aug S ep Oct Nov Dec Month

-*- Pup Weight a Adults Provisioned -o- Adult Weight M I Pups Provisioned

FIG. 1.-Mean weight of island fox pups in relation to mean weight of adult foxes and percentage of captures in which provisioning occurred per age class per month. Adult and pup weights are shown with standard error bars, and all weight data are from Santa Cruz Island, California. year-round basis, but the greatest effort was focused culus) were found in 21 instances and birds from June through when island fox pups August, were found on the remaining three occasions. were making excursions from their dens. Single Two prey items were found seven times and door, welded-wire cage traps (Tomahawk, Wiscon- three prey items were found once. In an ad- sin) measuring 23 by 23 by 66 cm were placed in ditional 11 cases, were found outside traps grid configurations or as transects along roads or prey adult (six canyons, baited with dry cat food and a fruit scent, containing foxes female, four male, checked each morning, and then reset. Pups were and one undetermined). In 10 of the 11 cases differentiated from adults by mass and the presence the prey items were mice, and the remaining of deciduous teeth. case included two island night lizards (Xantusia Chi-square analysis was used to test for the effects riversiana). of season on the occurrence of found outside prey were found outside of traps of traps. Seasons were based on the developmental Prey containing pups the period prior to pups at- period of pups and are defined as the pup depen- only during adult mass (Fig. which corresponds dency period, May (when pups first venture from taining 1), dens) through August (when they approach adult to the pup dependency period. Nineteen pro- mass), and the non-dependency period, September visioning events were recorded between the through April. months of May and August during 8,302 trap On three days 1996, we provided food during July nights over nine years of trapping on San Cle- bread and for a pair of foxes (peanuts, raisins, jam) mente Island and four years of on with two pups to determine if the adults would pro- trapping Santa Cruz Island. was never ob- vision the pups. After presenting the food, we re- Provisioning corded the behavior of both the adults and pups. served during the non-dependency period, which included an additional 2,501 trap nights < RESULTS-On 24 occasions one or more prey on these two islands (x2 = 5.1; P 0.05). In items were found within ca. 10 cm of traps con- addition, we have observations of pups accom- taining island fox pups (2.1% of 1,135 pup panying foraging adults on 10 occasions, and captures). Either deer mice (Peromyscus mani- have captured pups with their presumed par- culatus) or introduced house mice (Mus mus- ents in the same trap on 22 occasions (15 with March 1999 Garcelon et al.-Food provisioning by island foxes 85 adult males, 7 with adult females) during the canids, prey items are carried back to the den, pup dependency period. Rate of provisioning or food is either given directly to or regurgi- was dependent on age class, with adults being tated for the pups. Wolf pups (Canis lupus) old provisoned significantly less frequently than enough to leave the area of their dens have pups (X2 = 32.3, P < 0.001). been reported with adults at rendezvous sites On 24 July, we offered 10 raisins, each pro- where they were provisioned (Mech, 1970). vided individually, to an adult female accom- Provisioning at or near den sites has been re- panied by a single pup. She consumed all of ported for several small to medium-sized North the raisins and was then offered a large piece American canids, including the red fox (Vulpes of bread covered with jam. The female moved vulpes-Zabel and Taggart, 1989), kit fox (Vul- off 5 m, then transferred the piece of bread to pes macrotis-Egoscue, 1962), swift fox (Vulpes the pup which he promptly consumed. On 25 velox--Uresk and Sharps, 1986) and arctic fox July the female and an adult male visited camp (Alopex lagopus-Garrott et al., 1983). However, with two pups, and in five offerings of jam-cov- we have found no reports of any canid species ered bread the female transferred each to one providing food to pups or mates caught in of the pups. The adult male ran off and con- traps. sumed the first bread he was offered, but trans- The occurrence of food items outside of ferred the second to the closest pup and the traps containing adult foxes could be a result third to the adult female. Later we observed of mate provisioning. The observation of food the female enter a bush carrying the piece of transfer from an adult male to an adult female bread she had received from the male, and af- supports the idea that mate provisioning oc- ter a few moments exited the bush without the curs, and the placement of food outside traps piece of bread and being followed by a pup. would only be an extension of that behavior. Although we had not witnessed a transfer, we The following points appear to support our believe that the female sought out and trans- hypothesis that prey had been brought to ferred the bread to the pup. Finally, on 27 July trapped foxes: 1) prey items were found out- the adult male visited our camp accompanied side traps only during the dependency period by a single pup. On this occasion we offered when fox pups averaged less than 70% adult 12 peanuts to the male and the pup in such a mass, 2) fox pups were observed accompany- way that the food items were approximately ing foraging adults, and were caught simulta- equidistant from each individual. Both individ- neously with their presumed parents, 3) mul- uals appeared to compete for these items and tiple prey items (2 to 3) were found outside the adult male procured 11 of the 12 peanuts. traps containing pups, and given the size of the These observations appear to suggest that combined prey compared to a pup's gape, it is adult foxes will provision pups with large but unlikely they could physically carry them, and not small food items. 4) adult foxes were observed transferring food The possible provisioning of a pup was ob- to pups in an artificial situation, and were also served on 8 June 1994 at a trap on San Cle- observed with food outside of a trap contain- mente Island. An adult female fox was present ing a pup. Therefore, we believe the presence outside a trap containing a pup, holding a of prey items found outside traps containing dead bird in her mouth. Another dead bird, a pups represents instances of provisioning and Gambel's quail chick (Callipepla gambelii), was further suggests that island foxes exhibit ex- already present outside the trap. Upon release tended biparental care, a behavior common to the pup and adult nuzzled and then moved a other canids. short distance away. The adult then returned to the trap, inspected it, picked up the bird she Research leading to these observations was sup- had previously been carrying, and departed ported by grants from the CaliforniaDepartment of the area with the bird. Fish and Game, United States Park Service, United States Navy,National Geographic Society (to GWR), Southern California Edison Company, and a Mil- DIscussioN-Provisioning has been reported dred Mathias Graduate Student Research grant (to for numerous large canids and parental care is GWR). We thank the Natural Resources Office, common in the Canidae (Moehlman, 1989; North Island Naval Air Station for permission to Packard et al., 1992; Thomson, 1992). In large work on San Clemente Island, The Nature Conser- 86 The Southwestern Naturalist vol. 44, no. 1 vancy for permission to work on Santa Cruz Island, of an endangered species. Natural History Press, and the United States Park Service for permission Doubleday & Company, Inc., New York. to work on San Miguel Island. The University of Cal- MOEHLMAN,P. D. 1979. Jackal helpers and pup sur- ifornia Reserve on Santa Cruz Island provided logis- vival. Nature 277:382-383. tical support. Helpful comments on the manuscript MOEHLMAN, P. D. 1989. 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