Prediction of Body Composition of Live and Post-Mortem Red Foxes

Abstract

A series of measurements (lengths, circumferences, skinfolds, masses and resistance) was taken on 29 red foxes (Vulpes vulpes) of both sexes before and after their death during the autumns of 1994 and 1995. Body composition of each carcass was determined by chemical analysis of homogenized samples of viscera, carcass and skin. Eight multiple regression models were then developed to predict body water, fat, protein, and mineral mass using body measurements as independent variables taken on live or dead animals. All final models were highly significant (P Ͻ 0.0001) and included three or four explanatory variables. Adjusted coefficients of determination varied between 0.95 for water mass and 0.81 for mineral mass. The models cover a wide range of conditions as percent body fat in the 29 samples varied between 1.1 and 28.4%. Our models can serve for management or research purposes with live or dead red foxes as they are quick, inexpensive and nondestructive.

Indices Using External Measurements for Assessing Fat Deposition of Adult Feral Raccoons (Procyon lotor) in Kanagawa Prefecture, Japan

“…Furthermore, the BMI of feral raccoons was found to correlate positively with seasonal changes of serum leptin, which is considered a marker of nutritional condition [36]. Because variations in body size in individuals affect BW, a standardized index based on body size was developed for assessing body fat deposition in mammals [5,15,18,27,30,33]. Nevertheless, Pitt et al [31] reported that the best index, which is characterized by a modified ratio of body mass to length (body mass/BL 2 ), explained only 62% of the observed variation in fat determined using BIA for raccoons; thus, morphological condition indices alone were concluded to be unsatisfactory for estimating body condition.…”

“…The most accurate index of body fat deposition is considered to be the amount of stored lipids, which can be quantified by direct chemical analysis of homogenates prepared from whole carcasses [4,9,10,18,27,34,40]. Despite having high accuracy, this method is expensive and time consuming, and it is not suitable for the rapid examination of a large number of samples.…”

“…In recent years, bioelectrical impedance analysis (BIA) has been introduced for estimating body fat deposition in the American black bear (Ursus americanus) [9,17,30], Brown bear (U. arctos) [9,17], Polar bear (U. maritimus) [3,9], and red fox (V. vulpes) [27]. In addition, several studies have evaluated body fat deposition using non-lethal methods based on the relationship between external and fat deposit measurements in a number of wild mammal species, including the American black bear [5,30], red fox [27], coyote (Canis latrans) [18], and Tsushima leopard cat (Prionailurus bengalensis euptiluurus) [15].…”

“…In addition, several studies have evaluated body fat deposition using non-lethal methods based on the relationship between external and fat deposit measurements in a number of wild mammal species, including the American black bear [5,30], red fox [27], coyote (Canis latrans) [18], and Tsushima leopard cat (Prionailurus bengalensis euptiluurus) [15].…”

“…Furthermore, portable BIA equipment, which was used in several previous studies [3,9,17,27,30,31], is not readily available in Japan, so BIA methods for measuring body fat deposition are not currently suitable for wildlife management here. In fact, although over 1,000 raccoons per year have been captured in efforts to reduce the feral raccoon population size in Kanagawa Prefecture [23], BIA or other specialized methods have not been used for examination of body fat deposition for any of the captured raccoons.…”