Staying cool: the importance of shade availability for tropical ectotherms

Chou, Chun-Chia; Perez, Daniela M.; Johns, Sophie; Gardner, Rachel R.; Kerr, Kecia A.; Head, Megan L.; McCullough, Erin L.; Backwell, Patricia R. Y.

doi:10.1007/s00265-019-2721-9

Cited by 20 publications

(18 citation statements)

References 45 publications

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“…There was a strong effect of distance on the number and the proportion of wave types. Conspecific crabs elicited more single waves when they were close to the focal male and more double waves when they were further away from the focal male, which is supported by recent findings that males give more double waves in low densities (Chou et al, ). The proportion of double waves was lower when heterospecific males (as opposed to conspecific males) were presented at greater distances, suggesting that double wave may act as a “broadcast” signal (given its higher amplitude).…”

Section: Discussionsupporting

confidence: 72%

The functions of multiple visual signals in a fiddler crab

Perez

Backwell

2019

Ethology

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In many species, it is common for animals to have multiple signals within one channel of communication. Multiple signals may, however, be inefficient if they are redundant in nature. Identifying the functional significance of these multiple signals is therefore important if we are to understand the evolution of such elaborated behaviours. We proposed to identify the roles of movement‐based multiple signals in a model animal system. Male fiddler crabs wave their sexually dimorphic enlarged claw during social interactions. Some species present multiple signals, where the level of complexity of the movement changes. Males of Austruca mjoebergi can perform a double wave consisting of a high‐ followed by a low‐elevation lifting of the claw, or a single wave consisting of the high‐elevation movement alone. We first investigated structural differences between the double and single wave types, and found that single waves were lower in elevation than double waves. We then explored the adaptive meaning of the wave types by manipulating the social context in which males wave. We found that double waves were given in all contexts and in higher proportions at long distances, suggesting a function of broadcasting male location. Single waves, on the other hand, were mainly given at close range and in the presence of conspecifics, suggesting intraspecific communication. Female presence elicited the highest number and proportion of single waves, a likely result of a female preference for higher wave rates. Finally, we point out that there is an element of interaction between wave types that deserves future attention. This paper is an important contribution to expand our understanding of the adaptive meaning of multiple visual signals and help reach a unified theory of their evolution.

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Section: Discussionsupporting

confidence: 72%

The functions of multiple visual signals in a fiddler crab

Perez

Backwell

2019

Ethology

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“…Males that are actively courting females may experience high body temperatures if they are displaying in open habitats where they can be seen or higher in the intertidal where females prefer the more stable burrows [ 53 , 65 ]. However, courting males also crowd into shaded areas that give them a thermal advantage [ 29 , 66 , 67 ], and those actively defending burrows have ready access to a cool microclimate. Hence, individual courting males may experience higher or lower than expected T b depending on local conditions, including the availability of shade, female habitat preferences, and variation in the intensity of sexual competition.…”

Section: Discussionmentioning

confidence: 99%

“…During the daytime low tide exposure period, M. panacea spends around a quarter of its time in a burrow during the non-breeding season but nearly half of its time there while breeding [ 30 ]. The fiddler crab Austruca mjoebergi is almost as likely to be in its burrow as it is feeding on the surface when its burrow is in the sun, but time in the burrow drops dramatically in shade, where it is more than three times as likely to be feeding on the surface [ 67 ]. The fact that crabs spend less time in burrows when those burrows are shaded suggests a costly tradeoff between feeding, courtship, and thermoregulation, costs that may increase for M. pugnax during the reproductive season when it experiences declines in fat stores [ 68 ].…”

Section: Discussionmentioning

confidence: 99%

Field-based body temperatures reveal behavioral thermoregulation strategies of the Atlantic marsh fiddler crab Minuca pugnax

et al. 2021

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Behavioral thermoregulation is an important defense against the negative impacts of climate change for ectotherms. In this study we examined the use of burrows by a common intertidal crab, Minuca pugnax, to control body temperature. To understand how body temperatures respond to changes in the surface temperature and explore how efficiently crabs exploit the cooling potential of burrows to thermoregulate, we measured body, surface, and burrow temperatures during low tide on Sapelo Island, GA in March, May, August, and September of 2019. We found that an increase in 1°C in the surface temperature led to a 0.70-0.71°C increase in body temperature for females and an increase in 0.75-0.77°C in body temperature for males. Body temperatures of small females were 0.3°C warmer than large females for the same surface temperature. Female crabs used burrows more efficiently for thermoregulation compared to the males. Specifically, an increase of 1°C in the cooling capacity (the difference between the burrow temperature and the surface temperature) led to an increase of 0.42-0.50°C for females and 0.34-0.35°C for males in the thermoregulation capacity (the difference between body temperature and surface temperature). The body temperature that crabs began to use burrows to thermoregulate was estimated to be around 24°C, which is far below the critical body temperatures that could lead to death. Many crabs experience body temperatures of 24°C early in the reproductive season, several months before the hottest days of the year. Because the use of burrows involves fitness trade-offs, these results suggest that warming temperatures could begin to impact crabs far earlier in the year than expected.

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“…Males that are actively courting females may experience high body temperatures if they are displaying in open habitats where they can be seen or higher in the intertidal where females prefer the more stable burrows ([49]; [50]). However, large courting males also crowd into shaded areas that give them a thermal advantage ([23]; [51]; [52]), and those actively defending burrows have ready access to a cool microclimate. Hence, individual courting males may experience higher or lower than expected T b s depending on local conditions, including the availability of shade, female habitat preferences, and variation in the intensity of sexual competition.…”

Section: Discussionmentioning

confidence: 99%

“…During the daytime low tide exposure period, M. panacea spends around a quarter of its time in a burrow during the non-breeding season but nearly half of its time there while breeding ([24]). The fiddler crab Austruca mjoebergi is almost as likely to be in its burrow as it is feeding on the surface when its burrow is in the sun, but time in the burrow drops dramatically in shade, where it is more than three times as likely to be feeding on the surface ([52]). The fact that crabs spend less time in burrows when those burrows are shaded suggests a costly tradeoff between feeding and thermoregulation, a cost that may increase for M. pugnax during the reproductive season when it experiences declines in fat stores ([53]).…”

Section: Discussionmentioning

confidence: 99%

Field-based body temperatures reveal behavioral thermoregulation strategies of the Atlantic marsh fiddler crabMinuca pugnax

Hews

Brodie

Allen

et al. 2020

Preprint

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AbstractBehavioral thermoregulation is an important defense against the negative impacts of climate change for ectotherms. In this study we examined the use of burrows by a common intertidal crab, Minuca pugnax, to control body temperature. To understand how body temperatures respond to changes in the surface temperature and explore how efficiently crabs exploit the cooling potential of burrows to thermoregulate, we measured body, surface, and burrow temperature data during low tide on Sapelo Island, GA in March, May, August, and September of 2019. We found that an increase in 1°C in the surface temperature led to a 0.70-0.71°C increase in body temperature for females and an increase in 0.75-0.77°C in body temperature for males. Body temperatures of small females were 0.3°C warmer than large females for the same surface temperature. Female crabs used burrows more efficiently for thermoregulation compared to the males. Specifically, an increase of 1°C in the cooling capacity (the difference between the burrow temperature and the surface temperature) led to an increase of 0.42-0.50°C for females and 0.34-0.35°C for males in the thermoregulation capacity (the difference between body temperature and surface temperature). The body temperature that crabs began to use burrows to thermoregulate was estimated to be around 24°C, which is far below the critical body temperatures that could lead to death. Many crabs experience body temperatures of 24°C early in the reproductive season, several months before the hottest days of the year. Because the use of burrows involves fitness trade-offs, these results suggest that warming temperatures could begin to impact crabs far earlier in the year than expected.

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Staying cool: the importance of shade availability for tropical ectotherms

Cited by 20 publications

References 45 publications

The functions of multiple visual signals in a fiddler crab

The functions of multiple visual signals in a fiddler crab

Field-based body temperatures reveal behavioral thermoregulation strategies of the Atlantic marsh fiddler crab Minuca pugnax

Field-based body temperatures reveal behavioral thermoregulation strategies of the Atlantic marsh fiddler crabMinuca pugnax

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