Dissertation

Physiological Flexibility of Free-Living Aardvarks (Orycteropus Afer) in Response to Environmental Fluctuations

Weyer, Nora Marie

2018

Overview

Aardvarks (Orycteropus afer) are ecological engineers because they dig the burrows that provide shelter for numerous sympatric animals and, as such, are keystone mammals in sub-Saharan Africa. They are nocturnally-active, solitary and elusive. As a result, aardvark ecophysiology is poorly understood, despite their ecological significance. Much of their range is becoming hotter and drier with global climate change, with potential impacts on the aardvarks. A recent drought in the Kalahari in the summer of 2012-13 coincided with high aardvark mortality. The Kalahari semi-desert at the south-western edge of aardvark distribution is the hottest and driest environment currently inhabited by aardvarks. Climate change will likely exacerbate the Kalahari’s harsh conditions through increased aridification and higher environmental temperatures. Whether the physiological plasticity of aardvarks will allow them to buffer such changes is unknown.I therefore studied wild, free-living aardvarks for ~3.5 years (July 2012 to September 2015) at Tswalu Kalahari Reserve, South Africa. Aardvarks were implanted with VHF-tracking units and data loggers to record body temperature and locomotor activity. Camera traps at burrows recorded the aardvarks’ times of emergence. I scored aardvark body condition and collected fresh scats for dietary analysis. Aardvarks typically feed exclusively on ants and termites, which depend largely on vegetation productivity. Thus, I assessed prey abundance and availability monthly using pitfall traps and signs of termite surface activity, and assessed vegetation productivity using field-based transect methods and remote-sensing data (MODIS-EVI). I subsequently measured energy and water content of the aardvarks’ main prey items.Harvester termites (Hodotermes mossambicus) were the most important dietary item for aardvarks throughout the study period, accounting for ~75 % of prey ingested, and providing ~90 % of water and energy needs. By contrast, research in less arid southern African regions found ants to be the dominant dietary item. Although the aardvarks’ regional flexibility in feeding on the most abundant social insects likely improves survival under normal conditions, aardvark well-being in the Kalahari might depend on fluctuations in harvester termite populations. I found that harvester termite abundance correlated with grass availability, which in turn depended on rainfall.During my study, inter-annual variability in rainfall was high; two good rainfall years occurred which had large amounts of rainfall early in the wet season, resulting in high vegetation productivity. During these years, ant (largely in summer) and termite abundances were high, thus aardvarks obtained sufficient prey to cover their minimum daily energy and water requirements, and were in good body condition. Irrespective of the season, aardvarks in good condition remained nocturnal, and were homeothermic, with a low 24-h amplitude of body temperature rhythm (~2.5 °C; varying from 35 to 37.5 °C). Their body temperature rhythm over 24-h closely tracked that of activity, with body temperature increasing at the beginning of the active phase, and declining at the end of the active phase.A drought during summer 2012-13 likely resulted in local declines of termite populations, such that aardvarks were no longer able to meet their energetic requirements. A mass mortality of aardvarks occurred at the end of the summer drought, and surviving aardvarks were in poor condition.

• Publisher: ProQuest Dissertations & Theses
• Subject: Body temperature / Climate Change / Deserts / Diet / Drought / Energy / Engineers / Entomology / Environmental conditions / Environmental science / Humor / Medicine / Meteorology / Physiology / Predation / Productivity / Rain / Rhythm / Seasons / Starvation / Summer / Surgery / Termites / Vegetation / Water Resources Management / Water shortages / Winter
• ISBN: 9798302196446