Abstract: the Annual and Seasonal Diet of the Bobcat (Lynx Rufus) Was Determined From

Abstract: The annual and seasonal diet of the bobcat (Lynx rufus) was determined from analysis of 188 feces in the Cape region of Baja California, Mexico, an arid zone with numerous subtropical elements in its flora and fauna. Bobcats fed mainly on lagomorphs, which reached 74% of occurrence, followed by rodents (40%), reptiles (15%), and birds (12%). No seasonal variations were observed. The results were consistent with those of studies elsewhere, indicating that bobcats still rely upon lagomorphs for much of their food in southern latitudes. This supports the hypothesis that lynx have evolved to prey on hares and rabbits. The prevalence of reptiles as prey of hohcats in our study area was the highest ever reported. They were reported as bobcat prey in only I of 20 studies from north of latitude 40°, but in 14 of the 18 studies carried out south of this latitude. With regard to feeding on reptiles, the habits of bobcats in Baja California Sur resemble those of other similar-sized felids in tropical areas, such as ocelots (Felis pardalis) and servals (Leptailurus servo!).

Résumé : L’analyse de 188 tbces recueillies dans la region du Cap, en Basse Californie, Mexique, une zone aride comptaot de nombreux éléments sub-tropicaux dans sa faune et sa fore, a permis de determiner les regimes alimentaires annuel et saisonnier du Lynx roux (Lynx rufus) dans la region. Les lynx se nourrissent surtout de lagomorphes, jusqu’b 74% du régime, de rongeurs (40%), de reptiles (15%) et d’oiseaux (12%). Aucune variation saisonnière n’a été enregistrée. Ces résultats concordent avee ceux obtenus en d’autres regions, ce qui semble indiquer que les lynx comptent surtout sur les lagomorphes comme proies aux latitudes australes. Ces données appuient l’hypothèse selon laquelle le lynx s’est adapté a chasser les lièvres et les lapins. La proportion de reptiles dans le régime alimentaire des lynx de cette region est Ia plus haute jamais signalée. Des reptiles ont été mentionnés dans le régime alimentairc du Lynx roux dans seulement l’une des 20 etudes connues au nord du 40° paralléle, mais daos 14 des 18 etudes connues au sud de cette latitude. En cc qui conceroe Ia consommation de reptiles, les habitudes des lynx de la Basse Californie se rapprochent de celles d’autres félins de taille semblable des regions tropicales, l’Ocelot (Felis pardalis) et le Serval (Leptoilurus serval). [Traduit par la Redaction]

Introduction range, and its diet is usually based on lagomorphs (hares and rabbits), although there is some geographical variation, deer Conspecific populations of widely distributed species will and (or) small mammals being important prey in some areas encounter geographical differences in the pressures that mold (McCord and Cardoza 1982; Maehr and Brady 1986). Up to their feeding behavior (Arnold 1981). Hence, we would expect nt)w, no information has existed on the food habits of this the regional diets of species having wide geographical distri felid in the southernmost part of its range, which is included butions to reflect the availability of different prey resources. in or neighboring the Neotropical region. The bobcat (Lynx rufus) is the most widely distributed The cat species of northern areas seem to be quite special native cat in North America, ranging from southern Canada ized in their diet, and Holarctic lynx species (genus Lynx, (approximately 52°N) to southern Mexico (17°N) (Anderson following Wilson and Recdcr 1993) are thought to have 1987). Its food habits are well known in many parts of this evolved to prey on Iagomorphs (Kurten 1968). ‘l’ropical felids, by contrast, usually take all the vertebrate taxa they can handle, Received June 7, 1996. Accepted October 7, 1996. especially reptiles (Emmons 1987; Kitchcner 1991). M. Delibes’ and S.C. Zapata. EstaciOn Bioldgica dc Doiiana, This paper reports the annual and seasonal diet of bobcats Consejo Superior de Investigaciones Cientificas (CS IC), in the Cape region of Baja California (Mexico), an area with Apartado 1056, Scvilla 41080, Spain. numerous suhtropical elements in its vegetation and fauna M.C. Blázquex. Estacidn BiolOgica dc DoAana, CSIC, (Goldman and Moore 1946). We expected that lagomorphs Apartado 1056, Sevilla 41080, Spain, and Ccntro de were important in the diet of Baja California bobcats (as they, tnvcstigaciones Bioldgicas dcl Norocste, Apartado 128, like other lynx species, have evolved to capture lagomorphs), La Paz 23000, Mexico. but also that reptiles would be more important here than else R. Rodriguez-Estrella. Centro de lnvcstigacioncs BiolOgicas where (owing to subtropical conditions in the area). To try dcl Norocstc, Apartado 128, La Paz 23000, Mexico, and to detect whether there is a latitudinal gradient in the impor EstaciOn lliológica de DoOana, CSIC, Apartado 1056, Sevilla tance of lagomorphs and reptiles as bobcat prey, we review 41080, Spain. 38 papers concerning the Ibod habits of this species in differ Author to whom all correspondence should be addressed. cnt areas.

Bobcats in Baja California belong to the subspecies Lynx consumed rodent, followed by the white-tooted mouse and rufus peninsularis and are reported to be the smaNest members desert wood rat. The California quail was the most frequent of the species (Thomas 1898; Samson 1979). Given the bird in the analyzed feces. Among reptiles, the spiny-tailed strong relationship between predator and prey sizes iguana was the predominant prey species. It ranked fourth in (Rosenzweig occurrence, exceeded only by the two leporids and the pocket 1966), especially in feuds (Leyhausen 1965), we expected mouse (Table 1). this small size to influence the kind of prey taken. No significant seasonal changes in prey composition were detected: bobcats fed primarily on rabbits and secondarily on Study area rodents in all seasons (Table 1). This lack of seasonal change in diet suggests that prey abundance and vulnerability do not Fieldwork was conducted in an area of about 10 km2 in and vary greatly during the year, which is characteristic of tropi around El Comitán, owned by the Centro de Investigaciones cal environments. Biológicas del Noroeste. It is a coastal lowland located 17 km north of La Paz City (24°17’N, 110°20’W). Soils are sandy loam, while the xerophytic sarcocaulescent scrub vegetation Discussion (Leon de Ia Luz et a!. 1996) is dominated by cardon cacti (Pachycereus pringlel), dagger cacti (Stenocereus gu,n,nosus), Lagomorphs occurred in most of the seats, with little varia tion between seasons, indicating that bobcats still rely upon mesquites (Prosopis articulara), palo verde trees (ercidiu,n them for much of their food near the southern limit of their microphyllurn), Adam’s trees (Fouquieria thguem), plum range. This is consistent with the results of most studies of (Cyriocarpa edulis), copales (Bursero spp.), lomboys bobcat diets, irrespective of latitude. Lagomorphs occurred (Jairopha cinerea), and chollas (Opunüa cholla). This kind in more than 30% of the samples (stomachs and (or) intestine of vegetation (“cardonal”) is very characteristic of the best preserved habitats in Baja California Sur. Mean annual rainfall and feces) in 30 (83%) of 36 studies of bobcat diets in areas is 150 mm, with precipiuition concentrated during the summer ranging from 48°N to 24°N (Table 2). Lagomorph remains were present in 49% or more of the samples in almost one- months, from July to September. Mean annual temperature is 23.9°C. half of these studies. In two cases only, they reached less than 10% occurrence, in each case being replaced by another mammal species, the mountain beaver (Aplodontia rufa; 74% Methods frequency of occurrence versus 7% for lagomorphs in 247 We collected bobcat feces (n 188) during 1994 by walking peri feces from Oregon; Witmer and deCalesta 1986) and white- odically along sandy paths and dry riverbeds. At least two females tailed deer (79% of occurrence in 43 feces collected during with kittens and some males were known to be living in the area the winter in Massachussetts, with only traces of leporids, during the study period. All of the area was covered regularly, so being found; McCord 1974). we considered the collected feces to be a representative sample of These results support Kurten‘s (1968) hypothesis concern those produced, although some were found in easily recognizable ing the evolution of the feeding specialization of lynx species clusters ( toilets” or fecal marking locations; Bailey 1972). Feces on lagomorphs. Nevertheless, rodents seem to be more impor were separated, labeled, and dried at 60°C until they reached a tant than rabbits as food of bobcats in the southern Appala constant dry mass. If possible, prey items were identified to species chians and western United States, and deer are also a notable by comparing hairs, teeth, feathers, scales, and bones with a refer prey of bobcats in the northeastern United States (Machr and ence collection. Results are presented as frequency of occurrence (number of occurrences of each prey type x 100 divided by the Brady 1986). number of fecal samples; this implies that the sum of frequencies Besides the fact that bobcats depend upon lagomorphs may be above 100). This method does not accurately reflect the even at subtropical latitudes, the most distinctive feature in mass of ingested material (e.g., Weaver 1993), but it is usually con the diet of bobcats in Baja California is the high frequency of sidered to give a good representation of food habits (Corbett 1989). occurrence of reptiles, which appeared in more than 15% of Samples were divided into four, according to season: winter the feces. The reptiles included at least two species of iguanas (January—March), spring (April—June), summer (July—September), and three species of snakes, one of them venomous (Table 1). and autumn (October—December). Numbers of occurrences were Both of the iguanas are relatively large, reaching 300 g in the compared among samples through a contingency-table analysis (G test; Sokal and Rohlf 1981). case of the spiny-tailed iguana. These were consumed also in winter, in spite of the fact that they have a short hibernation Results period in the area (Blázqucz and Ortcga-Ruhio 1996). Predation on reptiles by bobcats has been considered Prey items in bobcat feces from Baja California Sur included unusual elsewhere. In the review by Anderson (1987), reptiles at least 9 species of mammals, 7 birds, 5 reptiles, and 1 arthro were not even referred to as an occasional prey of the spe pod (Table 1). The most important prey category was lago cies, while in the reviews by McCord and Cardoza (1982) morphs, which occurred in 73.9% of the feces. Rodents were and Rolley (1987), it is stated that bobcats cat mammals and the second most important component of the diet, as they some birds, although in certain circumstances they can take occurred in 40. 1 % of the feces. Reptiles ranked third in almost anything available, including reptiles. importance (15.4% in occurrence), followed by birds (12.2%). Approximately 40% of the studies reviewed reported one Scorpions were also found. or more reptiles as prey of the bobcat (Table 2), including In the study area the predominani prey of the bobcat were snakes (51.4% of all identified reptiles; most were non- the jackrahbit and cottontail rabbit, consumed in about the venomous) aiid lizards (48.6%). The frequency of occurrence same proportions. The pocket mouse was the most frequently

Cc) t997 NRC Canada 480 Can. J. Zool, Vol. 75, 1997

Table 1. Seasonal diet (numbers of prey items) of bobcats from El Comitán, Baja California Sur, through analysis of feces.

Frequency of occurrence

Total Winter Spring Summer Autumn

(n = 188) (n = 74) (n = 49) (a = 24) (n = 41) G p

Mammals Lagomorphs Cottontail (Sylvilagus sp.) 28.2 Black-tailed jackrabbit (Lepus californicus) 26.0 Unknown lagomorph 19.7 Total lagomorphs 73.9 76.9 67.3 70.8 78.0 1.919 0.7 Rodents Antelope squirrel (Animosperniophilus leucurus) 1.6 Pocket gopher (Thoniornys sp.) Pocket 1.0 mouse (Chaetodipus sp.) Kangaroo rat 19.1 (Dipodomys merriami) White-footed 3.2 mouse (Peromyscus sp.) Desert wood 4.7 rat (Neotoma lepida) Unknown rodent 4.7 Total rodents 5.8 Others 40.1 39.0 38.7 41.4 41.4 1.778 0.7

Domestic cat (Fells catus) 0.5 1.3 0 0 0 — Total mammals 96.8 95.9 97.9 91.6 100 1.787 0.7 Birds American kestrel (Falco spa rverius 0.5 California quail (Callipepla calfornica) 4.2 White-winged dove (Zenaida asiatica) 1.1 Ground dove (Columbina passe rina) 1.1 Common flicker (Colaptes auratus) 1.1 Flycatcher (Myiarchus sp.) 1.6 Thrasher (Toxostoma sp.) 0.5 Unknown bird 2.1

Total birds 12.2 8.1 22.4 4.2 12.5 4.519 0.2 Reptiles Desert iguana (Dipsosaurus dorsalis) 2.1 Spiny-tailed iguana (Ctenosaura hemilopha) 5.3 Unknown lizard 1.6 Whipsnake (Masticophis flagellum) 1.1 Gopher snake (Pituophis melanoleucus) 2.1 Speckled rattlesnake (Crotalus mitchelli) 1.1 Unknown snake 2.1 Total reptiles 15.4 21.0 12.6 16.7 9.7 2.802 0.4 Arachnida Scorpion 1.1 0 0 0 4.8

Note: vi is the number of feces examined. of reptiles ranged between 0 and 15.4% (this study), hut cooler climates.” Likewise, Hernández et al. (1994) reported rarely exceeded 2%. A definite north to south trend was not the importance of reptiles and insects in the diet of coyotes detected, but reptiles were reported as bobcat prey in only I (canis lutrans) living in the arid Sonoran desert, and other of 20 studies carried out north of 40N, but in 14 of 18 studies authors (e.g., Bothma et al. 1984) have also reported earn carried out south of this latitude (Table 2). iVCOS feeding on reptiles in other deserts. This is North to south differences in predation upon reptiles could possibly due to the high species divcrsity and abundance of he related to changes in reptile abundance and the distribu reptiles in these areas, because of the increased solar ti()n of reptile sizes. A high incidence of reptiles in the diet radiation (Schall and Pianka 1978) and the high production of predators has been reported in desert areas at low lati effIciency of small ectotherms under these conditions (Turner tudes. In a pioneer study on the ecology of Saharan birds, Cf al. 1976). Valverde (1957) stated that “in hot climates, vegetarian rep Moreover, reptile abundance and diversity (and possibly tiles play the same role as prey of carnivores as rodents in total reptile biomass as well) increase toward the equator, independently of aridity (Schall and Pianka 1978; Zug 1993;

Table 2. Frequency of occurrence of Iagomorphs and reptiles in the bobcat diet in different states or provinces in North America, ordered approximately from north to south.

No. of feces Approx. No. of and intestinal Percentage with Percentage with latitude Geographic area stomachs samples lagomorphs reptiles (°N) Source Washington State 76 40 1) 48 Brittell et al. 1979 Washington State 404 27 0 48 Knick et al. 1984 Minnesota 50 37 0 48 Rollings 1945 Minnesota 73 40 0 48 Berg 1979 North Dakota 74 50 0 47 Trevor et al. 1989 Maine 88 22 0 45 Westfall 1956 Maine 170 51 0 45 Litvaitis et al. 1986a Maine 462 71 0 45 Litvaitis et al. l986b Maine 452 72 0 45 Dibello et al. 1990 Idaho 223 66 0 45 Baitey 1979 Idaho 160 36 0 45 Koehler and Hornocker 1991 Nova Scotia 662 71 0 45 Matlack and Evans 1992 Nova Scotia 113 47 54 0 44 Mills 1984 Vermont 140 31 0 44 Hamilton and Hunter 1939 Oregon 494 30 3 43 Toweill and Anthony 1988 Oregon 247 7 0 43 Witmer and deCalesta 1986 New Hampshire 388 49 0 43 Litvaitis et al. 1984 New York 208 60 0 42 Pollack 1951 Massachussetts 250 52 0 41 Potlack 1951 Massachussetts 43 2 0 41 McCord 1974 Utah 53 81 60 2 38 Gashwiler et a!. 1960 Virginia 107 124 55 2 37 Progulske 1955 Tennessee 15 34 35 0 36 Buttrey 1979 Tennessee 176 51 1 36 Story et al. 1982 California 1202 32 1 35 Sperry (in Young 1958) California 166 29 5 35 Leach and Frazier 1953 Oklahoma 57 ? 2 34 Sperry (in Young 1958) Oklahoma 145 39 0 34 Rolley and Warde 1985 Arkansas 150 39 2 34 Fritts and Sealander 1978 Arkansas 115 61 0 34 Tumlison and McDaniel 1990 Arizona 252 7 1 33 Sperry (in Young 1958) Arizona 176 38 1 33 Jones and Smith 1979 Alabama 137 218 34 2 33 Miller and Speake 1978 Texas 125 22 0 30 Beasom and Moore 1977 Florida 75 49 27 Fickett 1971 Florida 413 25 2 27 Maehr and Brady 1986 Durango 540 72 1 26 Delibes and Hiraldo 1987 Baja California 188 74 15 24 This study for North America see Currie 1991). This tendency is reflected latitudes with a greater number of hours of sunlight (Andrews in an analysis of the food of feral cas (Fells catus) on a 1982); hence, they would appear to be more rewarding in global scale (Fitzgerald 1988). That author found a signifi energetic terms to carnivores. The large spiny-tailed iguanas cant negative correlation bctween latitude and incidence of preyed upon in our study area belong to a subtropical species predation on reptiles: below 35°N, reptiles were usually found whose range is restricted to below 29°N. in more than 20% of cat stomachs and intestines, but above Some minor features in the diet of bobcats in Baja California 40°N they were found in no more than 10%. Also, bobcat- Sur arc also interesting. Several authors (Bailey 1972 and sized tropical Cats, such as ocelols (Fells pardalis) in South later works) have reported selectivity for cottontails in com America and servals (Leplailurus serval) in Africa, prey on parison with jackrabbits. Unfortunately, the availability of snakes and lizards regularly (Emmons 1987; Gccrtscma 1985). both species is unknown in our study area, but we saw jack- The relationship between low latitude and high incidence rabbits and their sign much more often than cottontails and of reptiles in the diets of carnivores could be related also to their sign, although both were consumed in approximately differences in the availability of medium-sized and large rep equal proportions. Thus, there could be also selectivity for tile species. On average, reptiles reach larger sizes at low cottontails in Baja California.

The rather high frequency of occurrence of small rodents, Bothrna, i. du P., Nel, J.A.J., and Mcdonald, A. 1984. Food niche such as the pocket mouse, and the lack of ungulate remains separation between four sympatrie Namib Desert carnivores. in the feces could be related to the small size of bobcats in J. Zool. (t965—l984), 202: 327—340. Baja California. In the southern and southwestern United Brittcll, J.D., Sweeney, S.J., and Kniek, S.T. 1979. Washington States and northern Mexico, rodents are important prey for bobcats: diet, population dynamics and movement. Inst. Wildl. bobcats (e.g., Beasom and Moore 1977; Miller and Speake Res. Natl. Wildi. Fed. Sei. Tech. Ser. No. 6. pp. 107—110. 1978; Jones and Smith 1979; Delibes and Hiraldo 1987), but Buttrey, G.W. 1979. Food habits and distribution of the bobcat medium-sized species (above 100 g mass), such as cotton rats (Lynx rufus) on the Catoosa Wildlife Management Area. Inst. WildI. Rcs. Natl. Wildl. Fed. Sci. Tech. Ser. No. 6. pp. 87—91. (Sigmodon spp.), wood rats (Neotorna spp.), and to a lesser Corbett, L.K. 1989. Assessing the diet of dingoes from feces: degree squirrels (Sciuridae), are consumed most often, whereas a comparison of 3 methods. J. Wildl. Manage. 53: 343—346. the smaller pocket mice and white-footed mice (under 30 g) Currie, D.J. 1991. Energy and large-scale patterns of animal- and are rarely captured. Maybe these small rodents are energeti plant-species richness. Am. Nat. 137: 25—49. cally rewarding for the small bobcats in the study area. Delibes, M., and Hiraldo, F. 1987. Food habits of the bobcat in two On the other hand, we did not find ungulates in the habitats of the southern Chihuahuan desert. Southwest. Nat. 32: analyzed feces. Usually, larger individual bobcats (adult 457 —461. males) take deer more often than smaller ones (females Dibello, F.J., Arthur, S.M., and Krohn, W.B. 1990. Food habits and juveniles; Litvaitis et al. 1986a). Hence, the small Baja of sympatric coyotes, Canis latrans, red foxes, Vulpes vulpes, and bobcats, Lynx rufus, in Maine. Can. Field-Nat. 104: 403 —408. California bob cats could be limited in their ability to Emmons, L.H. 1987. Comparative feeding ecology of feuds in a subdue these large prey. However, the scarcity of wild Neotropical rainforest. Behav. Ecol. Sociobiol. 20: 271 —283. ungulates (mule deer, Odocoileus hemionus) in our study Fickett, SB., Jr. 1971. Food habits data for the bobcat in Florida. area makes it impossible to resolve this issue. Florida Game and Freshwater Fish Commission, Federal Aid in Although the bobcat is considered one of the most studied Wildlife Restoration, Project No. W-4l-18. of all the wild felids (Kitchener 1991), more research in the Fitzgerald, B.M. 1988. Diets of domestic cats and their impact on south of its range would no doubt be very useful for a more prey populations. 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