Effects of Climate and Animal Density on Adult Sex Ratio Variation in a Large Herbivore
Adult sex ratio is often biased in natural populations, and its variation is known to influence different demographic components at the population level. The causes of variation in adult sex ratio remain, however, poorly understood. Using time series from 1979 to 2013, I investigated sex-specific ad...
Main Author: | |
---|---|
Other Authors: | , , , |
Format: | Master Thesis |
Language: | English |
Published: |
NTNU
2014
|
Subjects: | |
Online Access: | http://hdl.handle.net/11250/2351459 |
id |
ftntnutrondheimi:oai:ntnuopen.ntnu.no:11250/2351459 |
---|---|
record_format |
openpolar |
spelling |
ftntnutrondheimi:oai:ntnuopen.ntnu.no:11250/2351459 2023-05-15T15:12:22+02:00 Effects of Climate and Animal Density on Adult Sex Ratio Variation in a Large Herbivore Peeters, Bart Sæther, Bernt-Erik Bremset Hansen, Brage Ønvik Pedersen, Åshild Veiberg, Vebjørn 2014 http://hdl.handle.net/11250/2351459 eng eng NTNU ntnudaim:10171 http://hdl.handle.net/11250/2351459 41 Biologi Økologi atferd evolusjon og biosystematikk Master thesis 2014 ftntnutrondheimi 2019-09-17T06:51:01Z Adult sex ratio is often biased in natural populations, and its variation is known to influence different demographic components at the population level. The causes of variation in adult sex ratio remain, however, poorly understood. Using time series from 1979 to 2013, I investigated sex-specific adult population growth rates and mortality indices (based on carcass counts) of Svalbard reindeer (Rangifer tarandus platyrhynchus) to explain variation in adult sex ratio in response to climate variability and animal density. Food limitation due to harsh winter conditions and high animal density was expected to have a stronger effect on males relative to females due to a higher energy requirement related to body size and reproductive strategy. Accordingly, when accounting for the delayed effect of population-level fecundity (i.e. input from new cohorts) and the positive effect of summer temperature (directly determining vascular plant biomass), I found that increased winter precipitation (i.e. reduced forage accessibility) had a stronger negative effect on adult population growth rate in males than in females. Additionally, the mortality index increased more strongly in response to increased winter precipitation in males than in females. Increased winter precipitation, therefore, lead to a more female-biased ASR. High animal density, however, had a stronger negative effect on female adult population growth rate and increased the mortality index more strongly in females than in males, which could be related to sex-differences in density-dependent age structure. The present study is the first to demonstrate the effects of climate variability and animal density on adult sex ratio variation in an Arctic ungulate, which has important implications for management and harvest regimes of populations facing climate change. Master Thesis Arctic Climate change Rangifer tarandus Rangifer tarandus platyrhynchus Svalbard svalbard reindeer NTNU Open Archive (Norwegian University of Science and Technology) Arctic Svalbard |
institution |
Open Polar |
collection |
NTNU Open Archive (Norwegian University of Science and Technology) |
op_collection_id |
ftntnutrondheimi |
language |
English |
topic |
Biologi Økologi atferd evolusjon og biosystematikk |
spellingShingle |
Biologi Økologi atferd evolusjon og biosystematikk Peeters, Bart Effects of Climate and Animal Density on Adult Sex Ratio Variation in a Large Herbivore |
topic_facet |
Biologi Økologi atferd evolusjon og biosystematikk |
description |
Adult sex ratio is often biased in natural populations, and its variation is known to influence different demographic components at the population level. The causes of variation in adult sex ratio remain, however, poorly understood. Using time series from 1979 to 2013, I investigated sex-specific adult population growth rates and mortality indices (based on carcass counts) of Svalbard reindeer (Rangifer tarandus platyrhynchus) to explain variation in adult sex ratio in response to climate variability and animal density. Food limitation due to harsh winter conditions and high animal density was expected to have a stronger effect on males relative to females due to a higher energy requirement related to body size and reproductive strategy. Accordingly, when accounting for the delayed effect of population-level fecundity (i.e. input from new cohorts) and the positive effect of summer temperature (directly determining vascular plant biomass), I found that increased winter precipitation (i.e. reduced forage accessibility) had a stronger negative effect on adult population growth rate in males than in females. Additionally, the mortality index increased more strongly in response to increased winter precipitation in males than in females. Increased winter precipitation, therefore, lead to a more female-biased ASR. High animal density, however, had a stronger negative effect on female adult population growth rate and increased the mortality index more strongly in females than in males, which could be related to sex-differences in density-dependent age structure. The present study is the first to demonstrate the effects of climate variability and animal density on adult sex ratio variation in an Arctic ungulate, which has important implications for management and harvest regimes of populations facing climate change. |
author2 |
Sæther, Bernt-Erik Bremset Hansen, Brage Ønvik Pedersen, Åshild Veiberg, Vebjørn |
format |
Master Thesis |
author |
Peeters, Bart |
author_facet |
Peeters, Bart |
author_sort |
Peeters, Bart |
title |
Effects of Climate and Animal Density on Adult Sex Ratio Variation in a Large Herbivore |
title_short |
Effects of Climate and Animal Density on Adult Sex Ratio Variation in a Large Herbivore |
title_full |
Effects of Climate and Animal Density on Adult Sex Ratio Variation in a Large Herbivore |
title_fullStr |
Effects of Climate and Animal Density on Adult Sex Ratio Variation in a Large Herbivore |
title_full_unstemmed |
Effects of Climate and Animal Density on Adult Sex Ratio Variation in a Large Herbivore |
title_sort |
effects of climate and animal density on adult sex ratio variation in a large herbivore |
publisher |
NTNU |
publishDate |
2014 |
url |
http://hdl.handle.net/11250/2351459 |
geographic |
Arctic Svalbard |
geographic_facet |
Arctic Svalbard |
genre |
Arctic Climate change Rangifer tarandus Rangifer tarandus platyrhynchus Svalbard svalbard reindeer |
genre_facet |
Arctic Climate change Rangifer tarandus Rangifer tarandus platyrhynchus Svalbard svalbard reindeer |
op_source |
41 |
op_relation |
ntnudaim:10171 http://hdl.handle.net/11250/2351459 |
_version_ |
1766343057069834240 |