Comments on Guimarães & Sawaya. Pretending to be venomous: is a snake's head shape a trustworthy signal to a predator?

2011 ◽  
Vol 28 (1) ◽  
pp. 123-124 ◽  
Author(s):  
Janne K. Valkonen ◽  
Johanna Mappes
Keyword(s):  
Prey Species ◽  
Adaptive Significance ◽  
Predation Pressure ◽  
Olfactory Cues ◽  
Head Shape ◽  
Venomous Snake ◽  
Avian Predators ◽  
Empirical Experiment ◽  
Plasticine Models

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.

The yellow-legged gull as a predator of lizards in Balearic Islands

2014 ◽  
Vol 35 (2) ◽  
pp. 207-213 ◽  
Author(s):  
Valentín Pérez-Mellado ◽  
Mario Garrido ◽  
Zaida Ortega ◽  
Ana Pérez-Cembranos ◽  
Abraham Mencía
Keyword(s):  
Balearic Islands ◽  
Predation Pressure ◽  
Vertebrate Species ◽  
Sources Of Information ◽  
Mediterranean Islands ◽  
Lizard Species ◽  
Podarcis Lilfordi ◽  
Larus Michahellis ◽  
Plasticine Models ◽  
Different Sources

Lizards and gulls cohabit in several Mediterranean islands. The yellow-legged gull, Larus michahellis, was found to prey several vertebrate species. However, precise information about the interaction between gulls and other vertebrates, particularly with lizards is still scarce. The Balearic lizard, Podarcis lilfordi, shares several coastal islets with the yellow-legged gull. Using two different sources of information, we studied the interaction of both species in Colom Island (Menorca, Balearic Islands, Spain). We studied the diet of the yellow-legged gull and learnt that the Balearic lizard is not a common prey of the yellow-legged gull. On the other hand, we studied the potential predation pressure of gulls on lizards, using plasticine models of lizards. We did two different experiments from which we can conclude that yellow-legged gulls rarely attack lizards and, consequently, cannot be considered a major threat for this endemic lizard species, at least in the population under study. Finally, we obtained evidence that plasticine models can only be employed with caution to assess predation pressure of opportunistic scavengers, much as gulls are. The majority of marks on models were not the consequence of true attacks by gulls, but the result of ground exploratory behaviour of gulls in search of any edible matter. Therefore, contrary to popular belief, in the case of the yellow-legged gull, the proportion of marked models would be an indication of ground-based wandering activity, rather than a result of its predation pressure on lizards.

Food Resource Division Among Northern, Marine, Demersal Fishes

1972 ◽  
Vol 29 (7) ◽  
pp. 997-1003 ◽  
Author(s):  
A. V. Tyler
Keyword(s):  
Prey Species ◽  
Food Resource ◽  
Adaptive Significance ◽  
Irish Sea ◽  
Significant Heterogeneity ◽  
Predator Species ◽  
Passamaquoddy Bay ◽  
Marine Areas ◽  
Resource Division ◽  
Demersal Fishes

The division of food resources among 13 demersal fishes was examined over a 16-month period in an area of Passamaquoddy Bay, New Brunswick. Though over 100 prey species were found in the stomachs of the predators, each predator took only three or four principal prey, and these prey made up 70–99% of the mass of the food for each predator species. Which species that a predator took as principal prey depended on prey body size, whether the prey were nekton, epi-fauna, or in-fauna; and whether or not they had a hard test or shell. Within predator species there was significant heterogeneity in diet related to size of predator individual.The seasonal predators did not feed as a group on their own set of prey species. Most principal prey species of the seasonal predators were taken simultaneously by one or two of the regulars.Data were compared with published results from two other northern marine areas. Within Irish Sea, Sea of Okhotsk, and also Passamaquoddy winter and summer communities, only 10–24% of the possible recurrences of principal prey among predators actually occurred, i.e. there was relatively little overlap among diets. Such specialization would have adaptive significance in a food-limited production system.

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

2017 ◽  
Vol 284 (1847) ◽  
pp. 20162538 ◽  
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.

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

Insects ◽  
2018 ◽  
Vol 9 (4) ◽  
pp. 150 ◽  
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.

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

Ecology ◽  
2014 ◽  
Vol 95 (1) ◽  
pp. 56-67 ◽  
Author(s):  
J.-F. Therrien ◽  
G. Gauthier ◽  
E. Korpimäki ◽  
J. Bêty
Keyword(s):  
Small Mammal ◽  
Canadian Arctic ◽  
Predation Pressure ◽  
Avian Predators

Predator odour does not influence trappability of southern brown bandicoots (Isoodon obesulus) and common brushtail possums (Trichosurus vulpecula)

2010 ◽  
Vol 58 (5) ◽  
pp. 267 ◽  
Author(s):  
Valentina S. A. Mella ◽  
Christine E. Cooper ◽  
Stephen J. J. F. Davies
Keyword(s):  
Avoidance Response ◽  
Foraging Behaviour ◽  
Prey Species ◽  
Olfactory Cues ◽  
Trichosurus Vulpecula ◽  
Predator Odour

Predators cause changes in the behaviour of many prey species. This study investigated whether trappability of wild southern brown bandicoots (Isoodon obesulus) and common brushtail possums (Trichosurus vulpecula) was influenced by odour cues suggesting the presence of potential predators. Trapping success was compared between traps with predator scents and controls in two different experiments. The first measured trapping success of single clean traps, traps with unfamiliar herbivore (horse) odour and traps scented with predator (fox, cat, quoll and dingo) odours, while the second offered three choices (fox, dingo and clean traps) simultaneously. Frequency of capture of bandicoots and possums was not influenced by odour, mass or sex in either experiment. The lack of avoidance response observed in this study suggests that neither southern brown bandicoots nor common brushtail possums alter foraging behaviour in response to olfactory cues that suggest the presence of exotic or Australian predators. This is consistent with previous studies, which indicate that native Australian marsupials do not avoid predator odours.

scholarly journals The effect of macrophytic cover on survival of Palaemonetes pugio and P. vulgaris (grass shrimp) in the presence of predatory Fundulus heteroclitus (killifish)

2001 ◽  
Vol 70 (2) ◽  
pp. 61-71 ◽  
Author(s):  
Henry C. Merchant ◽  
Ritindra N. Khan ◽  
Robert E. Knowlton
Keyword(s):  
Overall Survival ◽  
Green Alga ◽  
Fundulus Heteroclitus ◽  
Prey Species ◽  
Grass Shrimp ◽  
Predation Pressure ◽  
Complex Nature ◽  
Alternative Prey ◽  
Palaemonetes Pugio ◽  
Shrimp Species

Effects of three different macrophytic covers and the presence of alternative prey on survival of grass shrimp (Palaemonetes pugio and P. vulgaris) subjected to predation by killifish (Fundulus heteroclitus) were studied in the laboratory. Overall, survival of P. vulgaris was significantly greater (82%) than that of P. pugio (70%). This difference in survival was attributed to the greater tendency of P. pugio to swim outside the covers, making it more vulnerable to predation. Both prey species responded similarly to the different cover conditions. Survival without cover (gravel substrate) was 48%. In cover provided by a plastic plant made to resemble Ambulia, 75% of the starting population survived. In cover furnished by field-collected specimens of the flat chlorophyte, Ulva, survival was 71%, compared to 98% survival in the branched green alga, Codium. Predation pressure on neither species was significantly enhanced or diminished by the presence of a second prey species. For both grass shrimp species, increased survival in Codium in the presence of the predator was attributed to the physically more complex nature of this macrophytic cover.

Cymbium spp. (Gastropoda: Mollusca) as bivalve predators at the tidal flats of the Banc d'Arguin, Mauritania

2005 ◽  
Vol 85 (4) ◽  
pp. 949-953 ◽  
Author(s):  
Wim J. Wolff ◽  
Francesc Montserrat
Keyword(s):  
Prey Species ◽  
Tidal Flats ◽  
Predation Pressure ◽  
Banc D’Arguin ◽  
Sandy Sediments ◽  
Banc D'arguin

Two species of the genus of large gastropods Cymbium were observed on the tidal flats of the Banc d'Arguin, Mauritania: C. pepo and C. tritonis. Average densities on a flat studied in detail were 0·0009 and 0·0014 individuals per m2, respectively. Both species leave the tidal flats in April and are absent until at least September. Their density on the tidal flats was maximal on sandy sediments. Probably the distribution of their prey species determines the distribution of Cymbium. Prey species observed were the bivalves Anadara senilis (97%), and an occasional Solen vagina and Venerupis sp. The annual predation pressure of Cymbium on intertidal Anadara was estimated to be <1%.

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

2010 ◽  
Vol 88 (1) ◽  
pp. 122-128 ◽  
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.

The right choice: predation pressure drives shell selection decisions in the hermit crab Calcinus californiensis

2018 ◽  
Vol 96 (5) ◽  
pp. 454-459 ◽  
Author(s):  
E. Arce ◽  
A. Córdoba-Aguilar
Keyword(s):  
Hermit Crab ◽  
Prey Species ◽  
Predation Pressure ◽  
Hermit Crabs ◽  
Gastropod Shell ◽  
Selection Decisions ◽  
The Right

Several prey species use refuges to avoid predation. Prey need to abandon and shift between refuges. However, during such shifting, prey can be vulnerable to predators. We hypothesize that predator presence may induce prey to make mistakes in choosing their refuge. We tested this by inducing the hermit crab Calcinus californiensis Bouvier, 1898 to shift to a new empty gastropod shell (three different species: Columbella Lamarck, 1799, Nerita scabricosta Lamarck, 1822, and Stramonita biserialis (Blainville, 1832)) in the absence and presence of Eriphia squamata Stimpson, 1860, which is an efficient shell-crushing natural crab predator. We expected that when a predator was present, hermit crabs would (i) inspect fewer shells and (or) (ii) change to a shell that is either too heavy to allow escape or unfit in size to accommodate the hermit crab. Although the first prediction was met, the second prediction was supported only when S. biserialis shells were used. Thus, in the presence of a predator, hermit crabs prioritize escaping by selecting lighter shells, which would allow the crab to move faster. We conclude that predator presence may induce prey to make mistakes in refuge selection, suggesting that this has severe consequences in future predatory events.

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