Predation pressure by avian predators suggests summer limitation of small-mammal populations in the Canadian Arctic

Several species of non-venomous snake are known to flatten their heads when disturbed, and this behaviour has been suggested to be a mimicry of vipers (Arnold & Ovenden 2002, Hailey & Davies 1986, Young et al. 1999). Using plasticine models, Guimarães & Sawaya (2011) tested the antipredatory function of a triangular head shape in snakes. Their article presents the first published empirical experiment testing the adaptive significance of vipers' triangular head shape. Guimarães & Sawaya (2011) found no support for the viper mimicry hypothesis. Accordingly, they concluded that ‘the shape of [the] head seemed not to confer advantage itself’. Although the use of plasticine models is a generally accepted method of testing predation pressure on snakes, we argue that the experiment may have failed to find the antipredatory function of triangulation due to the pooling of attacks by mammalian and avian predators. Mammals generally rely on olfactory cues during foraging. Plasticine has a strong odour which does not resemble the odour of any prey species. It is thus unlikely that mammals would treat snake replicas as true snakes.

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Tail regeneration after autotomy revives survival: a case from a long-term monitored lizard population under avian predation

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.2538 ◽

2017 ◽

Vol 284 (1847) ◽

pp. 20162538 ◽

Cited By ~ 11

Author(s):

Jhan-Wei Lin ◽

Ying-Rong Chen ◽

Ying-Han Wang ◽

Kuen-Chih Hung ◽

Si-Min Lin

Keyword(s):

Cost Benefit ◽

Predation Pressure ◽

Natural Conditions ◽

Tail Regeneration ◽

Tail Loss ◽

Avian Predators ◽

Predatory Birds ◽

The Cost ◽

Caudal Autotomy

Caudal autotomy in lizards has intrigued scientists for more than 100 years. Because of the relative lack of literature under natural conditions, the complicated association among field autotomy rate, real predation pressure, the long-term cost of tail loss, and the benefit of regeneration remains equivocal. In this study, we conducted a 7-year capture–mark–recapture (CMR) programme with a wild population of a sexually dichromatic lizard, Takydromus viridipunctatus . We used autotomy indexes and a contemporary bird census mega-dataset of four predatory birds as predictors to examine the association between tail loss and predation pressure. We further estimated the survival cost of tail loss and alleviation by regeneration under natural conditions through CMR modelling. We found that large and small avian predators affect lizard survival through the following two routes: the larger-sized cattle egret causes direct mortality while the smaller shrikes and kestrels are the major causes of autotomy. Following autotomy, the survival rate of tailless individuals over the next month was significantly lower than that of tailed individuals, especially males during the breeding season, which showed a decline of greater than 30%. This sex-related difference further demonstrated the importance of reproductive costs for males in this sexually dichromatic species. However, the risk of mortality returned to baseline after the tails were fully grown. This study indicates the benefit of tail regeneration under natural conditions, which increases our understanding of the cost–benefit dynamics of caudal autotomy and further explains the maintenance of this trait as an evolutionarily beneficial adaption to long-term predator–prey interactions.

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Evaluating an Alleged Mimic of the Monarch Butterfly: Neophasia (Lepidoptera: Pieridae) Butterflies are Palatable to Avian Predators

Insects ◽

10.3390/insects9040150 ◽

2018 ◽

Vol 9 (4) ◽

pp. 150 ◽

Cited By ~ 1

Author(s):

Dale Halbritter ◽

Johnalyn Gordon ◽

Kandy Keacher ◽

Michael Avery ◽

Jaret Daniels

Keyword(s):

Danaus Plexippus ◽

Monarch Butterfly ◽

Predation Pressure ◽

Sister Species ◽

Conservation Priority ◽

Avian Predators ◽

Monarch Butterfly Danaus Plexippus ◽

Best Fit ◽

Migration Event ◽

Shed Light

Some taxa have adopted the strategy of mimicry to protect themselves from predation. Butterflies are some of the best representatives used to study mimicry, with the monarch butterfly, Danaus plexippus (Lepidoptera: Nymphalidae) a well-known model. We are the first to empirically investigate a proposed mimic of the monarch butterfly: Neophasia terlooii, the Mexican pine white butterfly (Lepidoptera: Pieridae). We used captive birds to assess the palatability of N. terlooii and its sister species, N. menapia, to determine the mimicry category that would best fit this system. The birds readily consumed both species of Neophasia and a palatable control species but refused to eat unpalatable butterflies such as D. plexippus and Heliconius charithonia (Lepidoptera: Nymphalidae). Given some evidence for mild unpalatability of Neophasia, we discuss the results considering modifications to classic mimicry theory, i.e., a palatability-based continuum between Batesian and Müllerian mimicry, with a quasi-Batesian intermediate. Understanding the ecology of Neophasia in light of contemporary and historical sympatry with D. plexippus could shed light on the biogeography of, evolution of, and predation pressure on the monarch butterfly, whose migration event has become a conservation priority.

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Predation on heliconia bugs, Leptoscelis tricolor: examining the influences of crypsis and predator color preferences

Canadian Journal of Zoology ◽

10.1139/z09-128 ◽

2010 ◽

Vol 88 (1) ◽

pp. 122-128 ◽

Cited By ~ 4

Author(s):

C. W. Miller ◽

S. D. Hollander

Keyword(s):

Natural Populations ◽

Predation Pressure ◽

Color Preference ◽

Color Variation ◽

Objective Measures ◽

Potential Prey ◽

Pressure Potential ◽

Color Preferences ◽

Color Saturation ◽

Avian Predators

Individuals in natural populations commonly vary in color, and such color variation can be important for survival under predation pressure. Potential prey may be more likely to survive when they are cryptic against their backgrounds. Alternatively, individual coloration, regardless of background, may itself best predict predation events. Few studies have simultaneously tested the importance of crypsis and predator color preferences in explaining predation events. In this study we used objective measures of coloration to examine whether heliconia bugs, Leptoscelis tricolor Westwood, 1842 (Hemiptera: Coreidae), resembling their background were less likely to be eaten by avian predators (crypsis hypothesis). Next, we evaluated whether insect color, irrespective of background, best explains predation events (color preference hypothesis). We found the strongest evidence for the crypsis hypothesis; predators chose prey that differed most from their background in color saturation. Some evidence was also found for the color preference hypothesis; predators avoided brightly colored prey. These results suggest that crypsis can be effective in detouring predation. However, when potential prey are detected, predator color preferences may best explain predation events.

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