Physiological and behavioural responses to temperature and humidity in fossorial amphibians

Amphibians have been the focus of research investigating physiological and behavioural responses to temperature and humidity for over two centuries. However, fossorial (i.e., underground-dwelling) amphibians remain comparatively understudied despite the unique environmental pressures that they experience. The overarching goal of this thesis was to understand how temperature and humidity affected the physiology and behaviour of fossorial amphibians. By combining phylogenetic methods and laboratory experiments, my chapters address the topics of energetics, hydroregulation, thermoregulation, and overwintering emergence. First, I tested the prevailing hypothesis that fossorial amphibians should have reduced metabolic rates compared to non-fossorial ones. My results did not support this hypothesis, highlighting that a reduction in amphibian metabolism would be evolutionary unlikely given the limited energetic benefit. Next, I assessed the effect of seasonal acclimatisation (spring versus autumn) on the thermal sensitivity of metabolism and water loss in Ambystoma maculatum. My findings suggested that acute changes in temperature affected energy and water budgets. However, acclimatory changes in temperature affected metabolism but not water loss. I then examined how temperature (17°C versus 22°C) influenced behavioural hydroregulation in A. maculatum. I found that salamanders defended a constant vapour pressure deficit between temperatures, which was achieved by targeting higher relative humidity at 22°C than at 17°C. This suggests that salamanders can detect their rates of evaporative water loss, and employ behaviours to limit increased evaporative demand at warmer temperatures. I also evaluated how behavioural thermoregulation differed between seasons (active versus overwintering), and found that A. maculatum engaged in active behavioural thermoregulation despite the prediction that fossorial ectotherms should show little thermoregulatory motivation. Lastly, I assessed how extrinsic (temperature and negative geotaxis) and intrinsic (migration restlessness) factors influenced overwintering emergence in A. maculatum. My results suggested that migration restlessness and negative geotaxis collectively influenced overwintering emergence, shedding light on how fossorial amphibians may navigate complex underground environments. Together, my chapters underscore the intricate coupling between physiology and behaviour in mediating how fossorial amphibians respond toshort- and long-term environmental variation.

Name thesis:degree_name

Ph.D. Biological Sciences

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Faculty of Mathematics and Science

Department dc:contributor.department

Department of Biological Sciences

Grantor dc:publisher

Brock University

Year dc:date.issued

2025

Author dc:creator

• Danilo Giacometti

Advisor dc:contributor.advisor

• Glenn Tattersall

• Amphibian
• Behaviour
• Hydroregulation
• Physiology
• Thermoregulation

Statement dc:rights

• Attribution-NonCommercial-NoDerivatives 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc-nd/4.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/10464/19426

OAI identifier oai:identifier

oai:brocku.scholaris.ca:10464/19426