J Anim Ecol. 2015 Nov 3. doi: 10.1111/1365-2656.12466. [Epub ahead of print]
Bastille-Rousseau G1, Schaefer JA1, Lewis KP2, Mumma M3, Ellington EH1, Rayl ND4, Mahoney SP2, Pouliot D5, Murray DL1.
Abstract
1.Climate
can have direct and indirect effects on population dynamics via changes
in resource competition or predation risk, but this influence can be
modulated by density- or phase-dependent processes. We hypothesized that
for ungulates, climatic conditions close to parturition have a greater
influence on the predation risk of neonates during population declines,
when females are already under nutritional stress triggered by food
limitation. 2.We examined the presence of phase-dependent
climate-predator interactions on neonatal ungulate survival by comparing
spatial and temporal fluctuations in climatic conditions, cause
specific mortality, and per capita resource limitation. We determined
cause-specific fates of 1384 caribou (Rangifer tarandus) from 10 herds
in Newfoundland, spanning more than 30 years during periods of numerical
increase and decline, while exposed to predation from black bears
(Ursus americanus) and coyotes
(Canis latrans). 3.We conducted Cox proportional hazards analysis for
competing risks, fit as a function of weather metrics, to assess pre-
and post-partum climatic influences on survival on herds in population
increase and decline phases. We used cumulative incidence functions to
compare temporal changes in risk from predators. 4.Our results support
our main hypothesis; when caribou populations increased, weather
conditions preceding calving were the main determinants of
cause-specific mortality, but when populations declined, weather
conditions during calving also influenced predator-driven mortality.
Cause-specific analysis showed that weather conditions can
differentially affect predation risk between black bears and coyotes
with specific variables increasing the risk from one species and
decreasing the risk from the other. 5.For caribou, nutritional stress
appears to increase predation risk on neonates, an interaction which is
exacerbated by susceptibility to climatic events. These findings support
the phase-dependent climate-predator (PDCP) interactions framework,
where maternal body condition influences susceptibility to
climate-related events and, subsequently, risk from predation. This
article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
