R. Villafuerte et al., PHYSIOLOGICAL-RESPONSES BY LAGOMORPHS TO RESOURCE LIMITATIONS IMPOSEDBY HABITAT FRAGMENTATION - IMPLICATIONS FOR CONDITION-SENSITIVE PREDATION, Canadian journal of zoology, 75(1), 1997, pp. 148-151
Human land uses have resulted in landscape mosaics with habitat patche
s that vary in quality. Patch quality (including the abundance of food
and the risk of predation) can affect the survival of animals that ar
e sequestered in remnant patches of habitat. Recent investigations of
the demography of New England cottontails (Sylvilagus transitionalis)
have shown that cottontails on small (resource poor) patches were in p
oor physical condition (based on body mass) and often foraged at sites
with limited cover. This resulted in a higher mortality rate than amo
ng rabbits occupying large (resource rich) patches. To gain additional
insight into the consequences of habitat fragmentation, we tracked th
e physiological condition of rabbits occupying small and large patches
during winter. The physiological condition of rabbits was determined
using the urinary urea nitrogen:creatinine ratio, and the results were
compared with similar indices obtained from captive rabbits. Consiste
nt with our expectations, the nitrogen:creatinine ratios indicated tha
t rabbits on small patches were nutrient limited for a longer period t
han rabbits on large patches. Transmitter-equipped rabbits on small pa
tches had a lower survival rate and died earlier than rabbits on large
patches. All mortalities were predator related. Using these data, we
developed a simple model that supports the role of ''condition-sensiti
ve predation'' as a major factor limiting populations of New England c
ottontails. Our results also demonstrate the utility of sampling physi
ological condition to provide an index of quality of lagomorph habitat
in human-dominated landscapes.