Leech removal is not the primary driver of basking behavior in a freshwater turtle

McKnight, Donald T., Wirth, Wytamma, Schwarzkopf, Lin, and Nordberg, Eric J. (2021) Leech removal is not the primary driver of basking behavior in a freshwater turtle. Ecology and Evolution, 11 (16). pp. 10936-10946.

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Abstract

Leaving the water to bask (usually in the sun) is a common behavior for many freshwater turtles, with some species also engaging in “nocturnal basking.” Ectoparasite removal is an obvious hypothesis to explain nocturnal basking and has also been proposed as a key driver of diurnal basking. However, the efficacy of basking, day or night, to remove leeches has not been experimentally tested. Therefore, we examined the number of leeches that were removed from Krefft's river turtles (Emydura macquarii krefftii) after experimentally making turtles bask at a range of times of day, durations, and temperatures. Turtles had high initial leech loads, with a mean of 32.1 leeches per turtle. Diurnal basking under a heat lamp for 3 hr at ~28°C significantly reduced numbers of leeches relative to controls. In diurnal trials, 90.9% of turtles lost leeches (mean loss of 7.1 leeches per turtle), whereas basking for 30 min under the same conditions was not effective (no turtles lost leeches, and all turtles were still visibly wet). Similarly, “nocturnal basking” at ~23°C for 3 hr was not effective at removing leeches. Only 18% of turtles lost leeches (one turtle lost one leech and another lost four leeches). Diurnal basking outdoors under direct sunlight for 20 min (mean temp = 34.5°C) resulted in a small reduction in leeches, with 50% of turtles losing leeches and an average loss of 0.7 leeches per turtle. These results indicate basking can remove leeches if temperatures are high or basking durations are long. However, it was only effective at unusually long basking durations in this system. Our data showed even the 20-min period was longer than 70.1% of natural diurnal basking events, many of which took place at cooler temperatures. Therefore, leech removal does not appear to be the purpose of the majority of basking events.

Item ID: 70213
Item Type: Article (Research - C1)
ISSN: 2045-7758
Keywords: aerial basking, ectoparasite, parasite, reptile, thermoregulation
Copyright Information: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2021 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
Date Deposited: 19 Nov 2021 04:03
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310301 Behavioural ecology @ 33%
31 BIOLOGICAL SCIENCES > 3109 Zoology > 310914 Vertebrate biology @ 34%
31 BIOLOGICAL SCIENCES > 3103 Ecology > 310304 Freshwater ecology @ 33%
SEO Codes: 18 ENVIRONMENTAL MANAGEMENT > 1803 Fresh, ground and surface water systems and management > 180303 Fresh, ground and surface water biodiversity @ 100%
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