Food supplementation affects the foraging ecology of a low-energy, ambush-foraging snake

Glaudas, Xavier; Alexander, Graham J.

doi:10.1007/s00265-016-2239-3

Cited by 23 publications

(27 citation statements)

References 53 publications

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“…The model predicts that it is advantageous for ambush‐foraging snakes to down‐regulate digestive systems when not digesting since the energetic savings accrued exceed the resulting additional costs of up‐regulation (increased apparent specific dynamic action [SDA]; Secor, ). However, our meta‐analysis reveals that average meal size does not differ between ambush and active foragers, and several recent autecological studies using fixed videography—one of the least‐biased data collecting techniques because it directly records feeding events (Lewis, Fuller, & Titus, ; Reif & Tornberg, )—on ambush‐foraging snakes have shown that feeding is more frequent than previously thought for most species (Clark, ; Clark, Tangco, & Barbour, ; Glaudas & Alexander, ; Putman, Barbour, & Clark, ). These findings suggest that meal size and frequency may not be drastically different between feeding modes and thus raises questions about the basic assumptions regarding the selective forces that have resulted in digestive down‐regulation in ambush‐foraging snakes.…”

Section: Discussionmentioning

confidence: 53%

Foraging mode, relative prey size and diet breadth: A phylogenetically explicit analysis of snake feeding ecology

Glaudas

Glennon

Martins

et al. 2019

Journal of Animal Ecology

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Foraging modes (ambush vs. active foraging) are often correlated with a suite of morphological, physiological, behavioural and ecological traits known as the "adaptive syndrome" or "syndrome hypothesis." In snakes, an ecological correlate often reported in the literature is that ambush‐hunting snakes have a higher relative meal size compared to actively foraging snakes which feed on smaller prey items. This “large meal versus small meal” feeding hypothesis between ambush and active foragers has become a widely accepted paradigm of snake feeding ecology, despite the fact that no rigorous meta‐analysis has been conducted to support this generalization. We conducted a phylogenetically explicit meta‐analysis, which included ca. 100 species, to test this paradigm of snake feeding ecology. We gathered data on prey size by inducing regurgitation by palpation in free‐ranging snakes and by examining the stomach contents of preserved museum specimens. When we found prey, we recorded both snake and prey mass to estimate relative prey mass (prey mass/snake mass). We also reviewed published studies of snake feeding ecology to gather similar information for other species. Ambush and active foragers did not differ in minimum or average meal size but the maximum meal sizes consumed by ambush‐foraging snakes were larger than the maximum meal sizes eaten by active foragers. This results in ambush‐foraging snakes consuming a significantly wider range of meal sizes, rather than being large meal specialists compared to active foragers. We argue that ambush foragers evolved to be more opportunistic predators because they encounter prey less frequently compared to active foragers. This hypothesis is further supported by the fact that ambush foragers also exhibited marginally wider diet breadths, consuming a broader range of prey types in comparison with active foragers. Our study challenges aspects of the foraging syndrome as it is currently conceived, and our results have important implications for our understanding of how foraging mode has shaped the behaviour and physiology of ambush‐foraging snakes.

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Section: Discussionmentioning

confidence: 53%

Foraging mode, relative prey size and diet breadth: A phylogenetically explicit analysis of snake feeding ecology

Glaudas

Glennon

Martins

et al. 2019

Journal of Animal Ecology

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“…Wasko and Sasa () determined both sexes of terciopelos ( Bothrops asper ) that were food supplemented in a prey‐limited environment in Costa Rica did not differ in home range sizes, but supplemented snakes had shorter and less frequent movements than unfed controls. Glaudas and Alexander () found naturally foraging male puff adders ( Bitis arietans ) also did not differ in home range size but moved farther within defined home ranges to find ambush sites compared to food‐supplemented males. These results suggest that food supplementation may affect the movements of vipers in ways that vary geographically, temporally, and demographically.…”

Section: Discussionmentioning

confidence: 99%

“…This largely stationary foraging tactic may reduce the available time to move to find mates, as some male vipers feed during the breeding season (Tetzlaff, Ravesi, Parker, Forzley, & Kingsbury, 2015) or may even increase feeding frequency compared to the nonbreeding season (Webber, Glaudas, & Rodrıguez-Robles, 2012). As such, males of numerous snake species decrease feeding rates (Glaudas & Alexander, 2017) or fast (Daltry, Wuster, & Thorpe, 1998;Slip & Shine, 1988) during the breeding season, suggesting foraging may come at the expense of increasing reproductive opportunities for these species. Male snakes which have built up energy reserves from feeding could invest substantial effort into finding females, given the high energetic investment of reproduction (Bonnet & Naulleau, 1996;Olsson, Madsen, & Shine, 1997).…”

Section: Introductionmentioning

confidence: 99%

“…We accomplished this by supplementing the diets of male massasauga rattlesnakes (Sistrurus catenatus) with mice across an active season. Manipulating food resources has been a useful technique for observing behavioral responses of foraging, thermoregulation, movement, and reproduction for numerous terrestrial vertebrates (Bacigalupe, Rezende, Kenagy, & Bozinovic, 2003;Boutin, 1990), including snakes (Blouin-Demers & Weatherhead, 2001;Glaudas & Alexander, 2017;Taylor, Malawy, Browning, Lemar, & DeNardo, 2005;Wasko & Sasa, 2012). As food-supplemented males should have minimal or no need to allocate time to stationary foraging, we tested the prediction that these snakes would move more during the breeding season than males which were not food supplemented.…”

Section: Introductionmentioning

confidence: 99%

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To forage, mate, or thermoregulate: Influence of resource manipulation on male rattlesnake behavior

Tetzlaff

Carter

DeGregorio

et al. 2017

Ecology and Evolution

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Male animals should preferentially allocate their time to performing activities that promote enhancing reproductive opportunity, but the need to acquire resources for growth and survival may compete with those behaviors in the short term. Thus, behaviors which require differing movement patterns such as ambushing prey and actively searching for mates can be mutually exclusive. Consequently, males that succeed at foraging could invest greater time and energy into mate searching. We radio‐tracked sixteen male massasauga rattlesnakes (Sistrurus catenatus) and supplemented the diets of half the snakes with mice across an active season. We tested the predictions that reduced foraging needs would allow fed snakes to move (i.e., mate search) more, but that they would consequently be stationary to thermoregulate less, than unfed controls. Contrary to our first prediction, we found no evidence that fed snakes altered their mate searching behavior compared to controls. However, we found controls maintained higher body temperatures than fed snakes during the breeding season, perhaps because fed snakes spent less time in exposed ambush sites. Fed snakes had higher body condition scores than controls when the breeding season ended. Our results suggest the potential costs incurred by devoting time to stationary foraging may be outweighed by the drive to increase mating opportunities. Such instances may be especially valuable for massasaugas and other temperate reptiles that can remain inactive for upwards of half their lives or longer in some cases, and for female rattlesnakes that generally exhibit biennial or more protracted reproductive cycles.

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“…As part of a food supplementation study on adult male puff adders from 2013 to 2015 (Glaudas & Alexander, ), we offered pre‐killed striped mice ( Rhabdomys pumilio ), a natural prey species, for a 2‐month period to six individuals each year (18 individuals overall). We used radiotelemetry to locate the snakes, and fed them in situ from 8‐Jan to 13‐Mar in 2013, 15‐Jan to 7‐Mar in 2014, and 13‐Jan to 5‐Mar in 2015.…”

Section: Methodsmentioning

confidence: 99%

To hold or not to hold? The effects of prey type and size on the predatory strategy of a venomous snake

2017

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The dangerous prey hypothesis predicts that when predators can discriminate between harmless and dangerous prey, they should alter their predatory behavior according to the risk. Venomous snakes, which rely on an envenomating strike to kill prey, often feed on potentially dangerous prey such as rodents, and have the choice between two alternative strategies following a bite: they either hold onto prey until it is incapacitated, or release it immediately, relying on scent trailing to find the bitten prey. In this study, we combined observational and experimental data collected in the field in South Africa to test the hypothesis that prey type and size affected the predatory strategy of a venomous snake, the puff adder (Bitis arietans; Viperidae). Relative prey size, but not prey type, affected the snake's strategy: puff adders typically struck and held prey of small size (e.g., toads, small adult mice and shrews), but often struck and released larger prey (e.g., large adult mice and rats), presumably because retaliatory bites from the latter ones are more dangerous. Hence, puff adders discriminated according to prey size and adjusted their predatory strategy consequently. Contrary to the common belief that viperid snakes typically strike and release prey, our findings agree with empirical evidence found in the literature, that is, puff adders generally alter their predatory tactics based on prey size. Although a few laboratory studies have examined the theme of the present paper in other venomous snakes, our research was conducted in a natural setting and thus provides a better understanding of the factors used by predators to choose between alternative hunting strategies.

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Food supplementation affects the foraging ecology of a low-energy, ambush-foraging snake

Cited by 23 publications

References 53 publications

Foraging mode, relative prey size and diet breadth: A phylogenetically explicit analysis of snake feeding ecology

Foraging mode, relative prey size and diet breadth: A phylogenetically explicit analysis of snake feeding ecology

To forage, mate, or thermoregulate: Influence of resource manipulation on male rattlesnake behavior

To hold or not to hold? The effects of prey type and size on the predatory strategy of a venomous snake

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