Diet, dietary selectivity and density of South American grey fox, Lycalopex griseus, in Central Chile.
The South American grey fox Lycalopex griseus is a canid widely distributed in southern South America; however, some aspects of its biology are still poorly known. We studied the diet and density of L. griseus in the Lago Peñuelas Biosphere Reserve, in Central Chile. The trophic niche breadth was B = 6.16 (Bsta = 0.47) and prey diversity was H' = 2.46 (Hmax ' = 3.17, J' = 0.78). The highest proportions of prey consumed in the diet were Oryctolagus cuniculus (52.21%) and other mammals (32.78%). We compared these results with a latitudinal gradient of diet results for this species in Chile. L. griseus eats mostly mammals (>90% of total prey), consuming the rodent Phyllotis darwini and reptiles in the northern zone; Oryctolagus cuniculus, Octodon degus and Abrocoma bennetti in the central zone; Abrothrix spp. and lagomorphs in the southern zone; and Lepus capensis and Ovis aries in the austral zone. The estimated density of L. griseus in Lago Peñuelas NR was 1.3 foxes/km2 .
Age determination in the dugong, Dugong dugon (Müller)
Abstract Growth layers in the dentine of about 75 dugong, Dugong dugon (Muller), unworn permanent incisor teeth have been examined with a view to absolute age determination. Thirteen of these teeth come from complete skulls which had previously been allocated relative ages within three arbitrary life stage groups (Mitchell, 1973). The layer numbers found range from zero to 57 1 2 , with a continuous scatter between the two extremes. It appears that the layers are either annual or biannual, and it is suggested that the dugong can attain an age of just under 60 or just under 30 years and reaches sexual maturity at about 10 or 5 years. A full account of this work is in preparation.
Functional feeding responses of coyotes, Canis latrans, to fluctuating prey abundance in the Curlew Valley, Utah, 1977-1993
We investigated interactions between coyotes (Canis latrans Say, 1823) and prey in the Curlew Valley, Utah, by comparing prey abundances with prey consumption rates. Previous studies reported a cyclic trend in black-tailed jackrabbit (Lepus californicus Gray, 1837) density with a period of 10 years and >150-fold amplitude, as well as short-term fluctuations among some rodent species that exceeded an 8-fold difference in amplitude over 2 years. Our results suggest changes in coyote diets mainly reflect the fluctuations in jackrabbit abundance. Prey switching to rodents during periods of low jackrabbit abundance also was evident. We used the initial feeding pattern analysis to compare prey consumption rates to prey abundance. Coyotes demonstrated a type II (hyperbolic) functional feeding response to changes in jackrabbit abundance. Functional feeding responses to rodent abundances were more difficult to assess because of the strong influence of jackrabbits. In most comparisons, we visually detected a linear...