In 9 trials, captive wolves (Canis lupus) were fed prey varying in size from snowshoe (Lepus americanus) to adult deer (Odocoileus virginianus), and the resulting scats were counted. collectible scats were distinguished from liquid, noncollectible stools. In collectible scats, the small prey occurred in greater proportion relative to the prey\u27s weight, and in lesser proportion to the prey\u27s numbers, than did the remains of larger prey. A regression equation with an excellent the data (r2 = 0.97) was derived to estimate the weight of prey eaten per collectible scat for With this information and average prey weights, the relative numbers of different prey eaten calculated

Floyd, Theodore J.

Jordan, Peter A.

Mech, L. David

English

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University of Nebraska - LincolnDigitalCommons@University of Nebraska - LincolnUSGS Northern Prairie Wildlife Research Center Wildlife Damage Management, Internet Center for1978RELATING WOLF SCAT CONTENT TOPREY CONSUMEDTheodore J. FloydUniversity of MinnesotaL. David MechUSGS Northern Prairie Wildlife Research Center, david_mech@usgs.govPeter A. JordanUniversity of MinnesotaFollow this and additional works at: https://digitalcommons.unl.edu/usgsnpwrcPart of the Animal Sciences Commons, Behavior and Ethology Commons, BiodiversityCommons, Environmental Policy Commons, Recreation, Parks and Tourism AdministrationCommons, and the Terrestrial and Aquatic Ecology CommonsThis Article is brought to you for free and open access by the Wildlife Damage Management, Internet Center for at DigitalCommons@University ofNebraska - Lincoln. It has been accepted for inclusion in USGS Northern Prairie Wildlife Research Center by an authorized administrator ofDigitalCommons@University of Nebraska - Lincoln.Floyd, Theodore J.; Mech, L. David; and Jordan, Peter A., "RELATING WOLF SCAT CONTENT TO PREY CONSUMED" (1978).USGS Northern Prairie Wildlife Research Center. 341.https://digitalcommons.unl.edu/usgsnpwrc/341 RELATING WOLF SCAT CONTENT TO PREY CONSUMED THEODORE J. FLOYD, Department of Entomology, Fisheries, and Wildlife, University of Minnesota, St. Paul 55108 L. DAVID MECH, U.S. Fish and Wildlife Service, Patuxent Wildlife Research Center, Laurel, Maryland 208111 PETER A. JORDAN, Department of Entomology, Fisheries, and Wildlife, University of Minnesota, St. Paul 55108 Abstract: In 9 trials, captive wolves (Canis lupus) were fed prey varying in size from snowshoe hares (Lepus americanus) to adult deer (Odocoileus virginianus), and the resulting scats were counted. Field- collectible scats were distinguished from liquid, noncollectible stools. In collectible scats, the remains of small prey occurred in greater proportion relative to the prey's weight, and in lesser proportion relative to the prey's numbers, than did the remains of larger prey. A regression equation with an excellent fit to the data (r2 = 0.97) was derived to estimate the weight of prey eaten per collectible scat for any prey. With this information and average prey weights, the relative numbers of different prey eaten also can be calculated. J. WILDL. MANAGE. 42(3):528-532 Scat analyses are widely used for de- termining food habits of carnivores. However, the degree to which the rela- tive frequencies of identifiable remains represent the actual proportion of prey types eaten is not known. Scott (1941) and Lockie (1959) considered this prob- lem with red fox (Vulpes vulpes) scat analyses and derived correction factors for converting weights of scats to actual weights of food eaten. Wolf scat analyses present more of a problem because of the great disparity in sizes and weight of prey eaten by wolves. Mech (1966, 1970) suggested that the oc- currence of remains of relatively small animals in wolf scats might overrepresent the proportion of those animals eaten compared with the remains of large mam- mals. This is because smaller animals, having a relatively high surface: volume ratio, would be covered with relatively more hair (the primary identifiable item in scats) per weight of flesh than would larger ones. Thus, a sample of wolf scats, 50 percent of which contained beaver (Castor canadensis) remains and 50 per- cent moose (Alces alces) remains, might actually mean that moose composed a higher proportion of the diet, in terms of weight, than did beavers. Pimlott et al. (1969) believed that wolf scat content accurately represented pro- portions of prey consumed, and Voigt et al. (1976) concurred, at least for deer fawns and beavers. Shelton (1966) agreed with Mech. Halverson (1969) thought that young animals were underrepresent- ed in scats compared to adults. Carbyn (1975) again stated the need for experi- mentation on this subject. The present study was conducted to test Mech's hypothesis and to establish criteria for interpreting from wolf scat data the relative ratios of prey types ea- ten. The study was supported by the USDA North Central Forest Experiment Station, the USDI Fish and Wildlife Ser- vice, the Ober Charitable Foundation, and the Agriculture Experiment Station, University of Minnesota. We also wish to thank B. Norton of the Duluth Zoo, J. Fletcher of the Como Zoo, St. Paul, and the Minnesota Department of Natural Resources for their cooperation, and T. Biebighauser for assisting with the data collection. T. Meier offered valuable sug- gestions for improving the presentation. ' Mailing address: North Central Forest Experi- ment Station, 1992 Folwell Avenue, St. Paul, Min- nesota 55108. 528 J. Wildl. Manage. 42(3):1978 PREY CONTENT OF WOLF SCATS *Floyd et al. 529 METHODS Carcasses of several species and sizes of prey were weighed and fed whole to groups of 3 to 5 captive yearling and adult wolves in 9 feeding trials from November 1975 to July 1976. The following prey types were used: snowshoe hares, wood- chucks (Marmota monax), beaver kit, beaver adult, whitetail deer fawn (4 types: 9.30 kg, 10.89 kg, 22.00 kg, and 39.01 kg), and adult white-tailed deer. Before each trial, the wolves were fasted for 36 to 48 h to clear their digestive sys- tems, and' all scats were removed from their pens. All wolves within a group consumed a single prey type in each trial. During each trial, scats were collected twice daily to minimize trampling and scattering. No further food was provided until scat production ceased. Uneaten re- mains, consisting mostly of hide and bone, were removed 36 to 48 h after the wolves ceased feeding on them and were weighed. Scats were classified as collec- tible (firm feces which would retain their form, endure weathering, and most likely would be collected in the field) and non- collectible (loose, liquid feces containing little identifiable material and unlikely to persist long enough to be collected in the field). For each prey type, we divided the weight of the prey eaten by the number of field-collectible scats that resulted. We then plotted the weight of prey per field- collectible scat against the weight of the prey type (Fig. 1). We also performed a regression analysis with these data and derived an equation describing the rela- tionship between the 2 parameters. RESULTS AND DISCUSSION The wolves completely consumed most of the carcasses except for the 3 heaviest deer, of which the remains Y 0.36 # 0.02 X S-.- 0.97 - Io 20 SI 4 C s 60 o10 9o io PREY WEIOnT (KO) Fig. 1. Relationship between the number of kg of prey per collectible scat (y) and the prey weight (x). ranged from 3.45 to 14.09 kg (Table 1). Scats appeared from 8 h after feeding be- gan until 56 h after it ceased. A high per- centage of the first scats deposited after feeding were of the liquid, noncollecti- ble type, but such scats were also depos- ited sporadically throughout the post- feeding period. Generally the fresh weight of the total scats resulting from a prey type was greater for heavier prey. However, lighter prey resulted in a pro- portionally greater total weight of feces than did heavier prey (Table 1), demon- strating that small prey is composed of a relatively greater proportion of undigest- ible matter. Another factor that became important with prey larger than medium-sized deer fawns was the proportion of uneaten re- mains of the prey. That increased with carcass weight (Table 1). Thus, with the heaviest carcasses, the lower scat produc- tion per kg of carcass eaten was even low- er. The total number of collectible plus noncollectible scats was relatively con- stant per kg of prey for all carcasses (Ta- ble 1), except for the 2 largest, of which substantial portions were left uneaten.However, the number of collectible scats per kg of prey eaten decreased as the size J. Wildl. Manage. 42(3):1978 530 PREY CONTENT OF WOLF SCATS *Floyd et al. Table 1. Results of feeding trials of captive wolves. Scats Weight Fresh weight (kg) Percent of No. per kg prey of prey (kg) Non- Non- Prey Collect- collect- Prey Prey Collect- collect- per trial Total Eaten ible ible Total weight eaten ible ible Total Snowshoe hares (9) 10.44a 10.44 1.24 1.05 2.29 21.9 21.9 2.11 1.05 3.16 Woodchucks (2) 2.84b 2.84 0.39 0.04 0.43 15.1 15.1 2.47 0.35 2.82 Beaver kit 3.40 3.40 0.48 0.48 14.1 14.1 2.06 2.06 Deer fawn 9.30 9.25 0.95 0.53 1.48 15.9 16.0 1.72 0.41 2.15 Deer fawn 10.89 10.87 1.12 0.06 1.18 10.3 10.9 1.56 0.18 1.74 Adult beaver 12.70 12.58 1.29 0.47 1.76 13.9 14.0 1.50 0.87 2.37 Deer fawn 22.00 18.55 1.67 1.80 3.47 15.8 18.7 1.50 1.14 2.64 Deer fawn 39.01 34.39 2.84 1.95 4.79 12.3 13.9 0.95 0.51 1.46 Adult deer 75.40 61.31 1.50 1.84 3.34 4.4 5.4 0.50 0.29 0.79 a Average weight per carcass = 1.16 kg. b Average weight per carcass = 1.42 kg. or weight of the prey increased (Table 1). This strong inverse relationship (r2 = 0.97) further indicated that smaller or lighter weight prey was composed of rel- atively more undigestible matter. This confirmed the hypothesis that, in terms of weight, small prey were overrepre- sented in frequencies of remains in wolf scats. So that the results of our feeding trials could be used to convert scat data to rel- ative weight and number of prey con- sumed, we derived a linear equation to describe the relationship between num- ber of collectible scats and weight of the prey consumed: y = 0.38 + 0.02x, where y is the kg of prey per collectible scat, and x, the average weight of an in- dividual of a given prey type (Fig. 1). This equation can be used to interpret wolf scat analysis data (Table 2). The pro- cess involves (1) estimating the average weight (x) of individuals of each prey type (deer fawn, doe, beaver, etc.), (2) solving the equation for y to determine the number of kg of prey per collectible scat for each prey type, and (3) multiply- ing e ch y by t e number of scats repre- senting the corresponding prey type in the total scat sample. Th  product gives he relative total weight of each type of prey fed upon. Then, by dividing these weights by the ave age weight for indi-viduals of each prey type, one can further derive the relative number of individuals of each type consumed, as representedby the scat sample. A hypothetical ex-ample using equal numbers of seats for each prey type demonstrates the use of this method (Table 2). An example from the literature illus- trates the difference the use of this tech- nique makes in interpreting scat data. Van Ballenberghe et al. (1975:1.2) found remains of adult deer in 219 spring and summer wolf scats, and remains of fawnsin 99 (31%) of the total scats with deer. Assuming that adult deer averaged 64 kg,and summer fawns 14 kg, y for adult deer is 1.66 kg per scat and for fawns, 0.66 kg pe  scat (Table 2). Multiplying these val- ues by the number of seats for each prey type gives 363.5 kg of adult deer con- sumed, and 65.3 kg of fawns. Thus, fawns J. Wildl. Manage. 42(3):1978 PREY CONTENT OF WOLF SCATS *Floyd et al. 531 Table 2. Hypothetical sample of wolf scats compared with estimated weight and number of individuals of each prey type eaten. Ratios of Assumed Prey Ratios of No. of number of Prey type weight of per scat (kg)a No. of Kg weight individuals individuals in scats prey (kg) (y) scats eatenb eatenc eatend eaten Adult deer 64.0 1.66 100 166.24 1.00 2.6 1.00 Deer fawn 14.0 0.66 100 65.34 0.39 4.7 1.81 Adult moose 409.0 8.56 100 856.24 5.15 2.1 0.80 Calf moose 91.0 2.20 100 220.24 1.32 2.4 0.93 Beaver 12.5 0.63 100 63.24 0.38 5.1 1.95 Snowshoe hare 1.2 0.41 100 40.64 0.24 33.9 13.03 a Calculated from the linear equation in Fig. 1. b Derived from the number of scats in the sample times the kg per scat. ' Relative ratios based on the adult deer as the primary unit. d Derived from the number of kg eaten divided by average weight of prey type. only represented about 15 percent of the total deer eaten. When the weights con- sumed are divided by the mean weights of adults and fawns, an estimate of 5.7 adult deer and 4.7 fawns eaten results. In terms of numbers of individuals con- sumed, then, fawns composed 45 per- cent. Both this and the hypothetical ex- ample (Table 2) show that with a direct proportional interpretation of scat analy- ses, small prey are overrepresented in terms of weight, and underrepresented in numbers. These disparities increase with prey whose sizes differ more than those of fawns and adult deer. To apply the present technique most accurately, one should use the actual number of scats containing each prey type, rather than the percentage of oc- currence, for some scats include remains of more than 1 prey type. Generally wolf scats each contain the remains of a single prey type. Thus, using this technique to convert percentage-of-occurrence data from wolf scats into proportions of prey types consumed will not produce too great an error. Certainly it will provide a more accurate interpretation than will direct projections of percentage-of-occur- rence data. For strictest accuracy, further refine- ments will often be necessary. Weights used for such rapidly growing prey types as deer fawns or moose calves should be adjusted for diff rent ag s, depending on when the wolf scats were deposited. Fur- thermore, since remains of yearling moose, for example, cannot be distin- guished from those of adults in wolf seats, average weights used for non-calvesshould be adjusted to consider relative proportions of yearlings and adults in the population of moose being killed by wolves.Application of this technique to seat analy s of smaller carnivores requires a further step because scats of those ani- mals often contain remains of 2 or more prey types. Thus, one must estimate what fraction of a scat contains each prey type. The total of all fractions of each prey type in an entire sample can be compared with that for the other prey types, and the present technique can then be applied. Neither Scott (1941) nor Lockie (1959) appeared to recognize the surface:volume ratio as a source of error in interpreting fox scat analysis data. However, the cor- rection factors derived by Lockie support the interpretation which our experiment has demonstrated. LITERATURE CITED CARBYN, L. N. 1975. A review of methodology and relative merits of techniques used in field stud- J. Wildl. Manage. 42(3):1978 532 PREY CONTENT OF WOLF SCATS. Floyd et al. ies of wolves. Pages 134-142 in Pimlott, D. H. ed. IUCN Pub. Supplementary Paper 43. Morges, Switzerland. 145pp. HALVERSON, P. B. 1969. Certain seasonal food habits of the timber wolf in northeastern Min- nesota with reference to wolf predation. Ma- calaster College Honors Paper. St. Paul, Minn. LOCKIE, J. D. 1959. The estimation of the food of foxes. J. Wildl. Manage. 23(2):224-227. MECH, L. D. 1966. The wolves of Isle Royale. U.S. Nat. Park Serv., Fauna Ser. 7:210pp. . 1970. The wolf; the ecology and behavior of an endangered species. Nat. Hist. Press, Doubleday, New York. xx + 389pp. PIMLOTT, D. H., J. A. SHANNON, AND G. B. KOLE- NOSKY. 1969. The ecology of the timber wolf in Algonquin Provincial Park. Ontario Dept. of Lands and Forests, Res. Rept. (Wildlife 87). 92pp. SCOTT, T. G. 1941. Methods and computation in fecal analysis with reference to the red fox. Iowa State Coll. J. Sci., 15:279-285. SHELTON, P. C. 1966. Ecological studies of beaver, moose, and wolf in Isle Royale National Park. Ph.D. Thesis, Purdue Univ., Indiana. 308pp. VAN BALLENBERGHE, V., A. W. ERICKSON, AND D. BYMAN. 1975. Ecology of the timber wolf in northeastern Minnesota. Wildl. Monogr. 43, 43pp. VOIGT, D. R., G. B. KOLENOSKY, AND D. H. PIM- LOTT. 1976. Changes in summer food habits of wolves in central Ontario. J. Wildl. Manage. 40(4):663-669. Received 19 January 1977. Accepted 13 February 1978. J. Wildl. Manage. 42(3):1978

RELATING WOLF SCAT CONTENT TO PREY CONSUMED

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RELATING WOLF SCAT CONTENT TO PREY CONSUMED

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