Ecology and conservation of wild giraffe in the northern Namib Desert

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Title: Ecology and conservation of wild giraffe in the northern Namib Desert
Authors: Hart, Emma E.
Permanent link: http://hdl.handle.net/10197/12817
Date: 2020
Online since: 2022-04-29T15:43:48Z
Abstract: The consequences of environmental change for threatened species are mediated by complex behaviours. Understanding how variation in environmental factors shapes animal behaviour is therefore key to modelling the adaptive responses of species to human or climate driven exogenous change. This places behavioural ecologists at the centre of wildlife conservation. Guided by this paradigm, the current research aims to inform the conservation of a threatened mega-herbivore, the giraffe, through investigation of the spatiotemporal drivers of giraffe behaviour. Chapter 1 frames the thesis in terms of how deficits in our understanding of the behavioural ecology of large herbivores remain limiting factors in their conservation. It provides background detail on the ecology of the study species and study area that are not included in the empirical chapters, as well as identifying gaps in our existing knowledge of the spatiotemporal drivers of giraffe behaviour. Chapter 2 addresses a historical difficulty in collecting accurate long-term and fine-scale movement data on wild giraffe. Both stationary and animal-borne trials across multiple geographical areas are used to test the precision and performance of a new solar-powered biotelemetry device. Results showed that the device had a high fix acquisition success rate, moderate precision error and a long functional lifespan, demonstrating how technological advances may be harnessed to address both the need to collect fine-scale movement data on terrestrial mammals and issues of animal welfare in biotelemetry research. Chapter 3 provides the first full picture of giraffe chronobiology by analysing 2.5 years of fine-scale movement data. Results revealed a diurnal, bimodal pattern, with locomotor activity peaking pre-dawn and again pre-dusk. Further analyses of the effects of solar and lunar zeitgebers demonstrated that giraffe locomotor activity increased pre-dawn during the hottest months of the year and decreased above a 30°C thermal threshold. These patterns suggest that the activity budgets of giraffe may be markedly restricted in the case of predicted rises in global temperatures. Finally, results revealed increased activity on moonlit nights (lunarphilia), providing some of the first evidence of the effect of the lunar cycle on the nocturnal activity patterns of large ungulates. Chapter 4 shifts the focus to the sociosexual drivers of giraffe behaviour. Results of analysis of a 3.5-year observational dataset revealed that giraffe bred year-round. However, further analyses of sexual segregation patterns and birth rates showed a possible hot-dry season conception pulse and a wet season birth pulse respectively, which were separated by a 15-month (giraffe gestation period) time-lag. Furthermore, results showed higher rates of juvenile survival for calves born before or during the wet season, suggesting a wet season birth pulse may convey a fitness advantage. In the context of climate change, these results highlight potential implications of phenological mismatch. Chapter 5 further investigates how social and environmental factors drive giraffe herd dynamics in a heterogeneous environment. Results showed that herd sex, but not the presence of juveniles, affected herd size. Further temporal analyses revealed increased herd sizes in the morning, but stable herd sizes year round. Finally, spatial analyses revealed consistently smaller herds in areas of relatively low resource abundance. These findings highlight the advantages of fission-fusion dynamics in the context of exogenous change, but also suggest that giraffe may be vulnerable to social fragmentation in habitats that do not support a certain threshold of resource abundance. Chapter 6 integrates the results, expanding on their conservation implications and underlining how they advance our understanding of the drivers of giraffe behaviour through space and time.
Funding Details: Giraffe Conservation Foundation (GCF)
Type of material: Doctoral Thesis
Publisher: University College Dublin. School of Biology and Environmental Science
Qualification Name: Ph.D.
Copyright (published version): 2021 the Author
Keywords: ConservationGiraffeGiraffa giraffaLarge herbivore
Language: en
Status of Item: Peer reviewed
This item is made available under a Creative Commons License: https://creativecommons.org/licenses/by-nc-nd/3.0/ie/
Appears in Collections:Biology and Environmental Science Theses

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