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The stress hormone corticosterone in a marine top predator reflects short-term changes in food availability.

ABSTRACT: In many seabird studies, single annual proxies of prey abundance have been used to explain variability in breeding performance, but much more important is probably the timing of prey availability relative to the breeding season when energy demand is at a maximum. Until now, intraseasonal variation in prey availability has been difficult to quantify in seabirds. Using a state-of-the-art ocean drift model of larval cod Gadus morhua, an important constituent of the diet of common guillemots Uria aalge in the southwestern Barents Sea, we were able to show clear, short-term correlations between food availability and measurements of the stress hormone corticosterone (CORT) in parental guillemots over a 3-year period (2009-2011). The model allowed the extraction of abundance and size of cod larvae with very high spatial (4 km) and temporal resolutions (1 day) and showed that cod larvae from adjacent northern spawning grounds in Norway were always available near the guillemot breeding colony while those from more distant southerly spawning grounds were less frequent, but larger. The latter arrived in waves whose magnitude and timing, and thus overlap with the guillemot breeding season, varied between years. CORT levels in adult guillemots were lower in birds caught after a week with high frequencies of southern cod larvae. This pattern was restricted to the two years (2009 and 2010) in which southern larvae arrived before the end of the guillemot breeding season. Any such pattern was masked in 2011 by already exceptionally high numbers of cod larvae in the region throughout chick-rearing period. The findings suggest that CORT levels in breeding birds increase when the arrival of southern sizable larvae does not match the period of peak energy requirements during breeding.

SUBMITTER: Barrett RT

PROVIDER: S-EPMC4377273 | biostudies-other | 2015 Mar

REPOSITORIES: biostudies-other

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The stress hormone corticosterone in a marine top predator reflects short-term changes in food availability.

Barrett Robert T RT Erikstad Kjell E KE Sandvik Hanno H Myksvoll Mari M Jenni-Eiermann Susi S Kristensen Ditte L DL Moum Truls T Reiertsen Tone K TK Vikebø Frode F

Ecology and evolution 20150226 6

In many seabird studies, single annual proxies of prey abundance have been used to explain variability in breeding performance, but much more important is probably the timing of prey availability relative to the breeding season when energy demand is at a maximum. Until now, intraseasonal variation in prey availability has been difficult to quantify in seabirds. Using a state-of-the-art ocean drift model of larval cod Gadus morhua, an important constituent of the diet of common guillemots Uria aa ...[more]

PMID: 25859335

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Project description:Effective management of wildlife populations rely on knowledge of their abundance, survival, and reproductive rates. Maintaining long-term studies capable of estimating demographic parameters for long-lived, slow-reproducing species is challenging. Insights into the effects of research intensity on the statistical power to estimate demographic parameters are limited. Here, we investigate implications of survey effort on estimating abundance, home range sizes, and reproductive output of Indo-Pacific bottlenose dolphins (Tursiops aduncus), using a 3-year subsample of a long-term, capture-recapture study off Bunbury, Western Australia. Photo-identification on individual dolphins was collected following Pollock's Robust Design, where seasons were defined as "primary periods", each consisting of multiple "secondary periods." The full dataset consisted of 12 primary periods and 72 secondary periods, resulting in the study area being surveyed 24 times/year. We simulated reduced survey effort by randomly removing one, two, or three secondary periods per primary period. Capture-recapture models were used to assess the effect of survey intensity on the power to detect trends in population abundance, while individual dolphin sighting histories were used to assess the ability to conduct home range analyses. We used sighting records of adult females and their calving histories to assess survey effort on quantifying reproductive output. A 50% reduction in survey effort resulted in (a) up to a 36% decline in population abundance at the time of detection; (b) a reduced ability to estimate home range sizes, by increasing the time for individuals to be sighted on ?30 occasions (an often-used metric for home range analyses) from 7.74 to 14.32 years; and (c) 33%, 24%, and 33% of annual calving events across three years going undocumented, respectively. Results clearly illustrate the importance of survey effort on the ability to assess demographic parameters with clear implications for population viability analyses, population forecasting, and conservation efforts to manage human-wildlife interactions.

Dataset Information

The stress hormone corticosterone in a marine top predator reflects short-term changes in food availability.

Publications

The stress hormone corticosterone in a marine top predator reflects short-term changes in food availability.

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