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Additional Adaptations Against Predation
Abstract
As butterflies, monarchs (Danaus plexippus) (Fig. 7.1) do not fight predators or act passively if an attack by a predator is imminent; instead, the monarch uses warning coloration and chemical defenses against predation. As adults, monarchs are brightly colored in orange, black, and white; they, therefore, stand out in the environment to a predator, much like the pattern of a poisonous coral snake (Micrurus fulvius) (Zug et al. 2001). What does the coloration of a monarch signal to a potential predator? That is unpalatable, so stay away. Monarch becomes unpalatable because of toxins that larvae feed upon in milkweed (Asclepias syriaca). These toxins are cardio glycosides, which elicits vomiting in birds that may feed upon them. Only two bird species, the black-headed oriole (Icterus abeillei) and the black-headed grosbeak (Pheucticus melanocephalus) are known to feed on monarch with no ill effect. In fact, the viceroy butterfly (Limenitis archippus) mimics the coloration of the monarch to offset predation on it, which is a form of mimicry known as Batesian.
... Fox squirrels commonly exhibit countershading, a pelage pattern where an animal is dorsally dark and ventrally light (Steele and Koprowski, 2001). Countershading may conceal animals from above and below, especially in well-lit environments (Caro, 2005), though evidence for countershading as an adaptive coloration is mixed (Kiltie, 1988;Ruxton et al., 2004;Yahner, 2012). Countershading is thought to be a more effective antipredator adaptation in marine environments, where predators swim above and below prey (Kiltie, 1988). ...
The color patterns of an animal’s pelage, feather, or skin serve a variety of adaptive functions; importantly, one function is concealment through background matching. In spatially and temporally heterogeneous environments, some species exhibit multiple distinct color patterns within a population (i.e., color polymorphism). The environmental drivers of color polymorphism are poorly understood. We used the polymorphic eastern fox squirrel (Sciurus niger ssp.; hereafter, fox squirrel) as a model species to investigate the role of environmental factors on pelage coloration. Building upon previous research that investigated the drivers of melanism, we measured fox squirrel pelage coloration across the visible light spectrum. Agouti-colored squirrels were positively associated with increased proportion of burned area in a fox squirrel dispersal buffer. Light-colored (less melanistic) squirrels were positively associated with increasing proportion of cropland in a fox squirrel dispersal buffer. We posit that agouti pelage is broadly adapted to a range of heterogeneous conditions created by fire. Conversely, croplands, once established, are relatively stable ecosystems which promote a consistently adaptive light-colored pelage morph. We suggest that in an increasingly human-dominated environment, spatially and temporally homogeneous processes, such as prescribed burning, may not sufficiently recreate environmental heterogeneity, which could result in lost pelage diversity.
It has long been known that the general colors and tones of animals tend to match their backgrounds (E. Darwin, 1794; Poulton, 1890). The adaptive significance of this has been borne out in numerous experimental studies (DiCesnola, 1904; Sumner, 1934, 1935; Isley, 1938; Popham, 1942; Dice, 1947; Turner, 1961; Kettlewell, 1956, 1973; Kaufman, 1974; Wiklund, 1975; Curio, 1976). There is also a good understanding of warning coloration (Cott, 1940; Wickler, 1968; Edmunds, 1974; Rothschild, 1975). However, the determinants of color pattern are poorly known, although it is known in a general way that the patterns and forms of animals are similar to their backgrounds (Poulton, 1890; Thayer, 1909; Cott, 1940; Wickler, 1968; Robinson, 1969; Edmunds, 1974; Fogden and Fogden, 1974). It is the purpose of this paper to explore the factors that determine color patterns under various specific conditions. The basic assumption is that a color pattern must resemble a random sample of the background seen by predators in order to be cryptic, and must deviate from the background in one or more ways in order to be conspicuous. As a result, the actual pattern evolved in a particular place represents a compromise between factors which favor crypsis and those which favor conspicuous color patterns.
Animal color patterns are a compromise between sexual selection pressures that increase advantages accrued from conspicuousness, and natural selection pressures that decrease those advantages through reduced survivorship. Predation pressure, as a mode of natural selection, often is invoked as a counter-selective force to sexual selection, yet few studies have demonstrated empirically that more conspicuous individuals experience higher rates of predation. We quantified predator attacks on models of collared lizards, Crotaphytus collaris, in three well-studied populations (Oklahoma, USA). These populations differ in coloration and in visual backgrounds against which the lizards are viewed by conspecifics and predators. Attack frequencies varied considerably among study sites but at all sites the models exhibiting the strongest color contrast with local rocks were detected and attacked most often. By comparison, inconspicuous models of females were never attacked at any of the sites. These results suggest a survival cost of conspicuous coloration in collared lizards, and reiterate the importance of considering the visual environment as well as differences among populations when examining the influence of predation on the evolution of animal color patterns.
Like humans engaged in risky activities, group members of some animal societies take turns acting as sentinels. Explanations
of the evolution of sentinel behavior have frequently relied on kin selection or reciprocal altruism, but recent models suggest
that guarding may be an individual's optimal activity once its stomach is full if no other animal is on guard. This paper
provides support for this last explanation by showing that, in groups of meerkats (Suricata suricatta), animals guard from safe sites, and solitary individuals as well as group members spend part of their time on guard. Though
individuals seldom take successive guarding bouts, there is no regular rota, and the provision of food increases contributions
to guarding and reduces the latency between bouts by the same individual.
All vectors of human malaria, a disease responsible for more than one million deaths per year, are female mosquitoes from the genus Anopheles. Evarcha culicivora is an East African jumping spider (Salticidae) that feeds indirectly on vertebrate blood by selecting blood-carrying female mosquitoes as preferred prey.
By testing with motionless lures made from mounting dead insects in lifelike posture on cork discs, we show that E. culicivora selects Anopheles mosquitoes in preference to other mosquitoes and that this predator can identify Anopheles by static appearance alone. Tests using active (grooming) virtual mosquitoes rendered in 3-D animation show that Anopheles' characteristic resting posture is an important prey-choice cue for E. culicivora. Expression of the spider's preference for Anopheles varies with the spider's size, varies with its prior feeding condition and is independent of the spider gaining a blood meal.
This is the first experimental study to show that a predator of any type actively chooses Anopheles as preferred prey, suggesting that specialized predators having a role in the biological control of disease vectors is a realistic possibility.
The intraspecific combat behavior of male muntjacs is described. Their antlers are found to be an essential instrument allowing tusk blows to be delivered during serious fights. A knowledge of the fighting behavior of muntjacs improves our understanding of the evolution of the aggressive behavior of male cervids and therefore of the origin and evolution of antlers.
As a suhsidiary result of a study on social behaviour of Thomson's gazelle in Serengeti National Park (Tanzania) there are given informations on flight behaviour and avoidance of predators. Alert posture, flight in galloping and stotting, and especially the relatively soft alarm call are more or less contagious and can release alertness or flight in conspecifics. Shaking of the flank (BROOKS, 1961) does not initiate flight only but galloping in general. It is the last link in a chain of actions which appears completed only in intraspecific situations. In perception of enemies the tommy reacts to optical stimuli from silhouettes and movements. The senses of smell and hearing are not so important in this context. If the tommies have recognized an enemy in time they try to keep it under control (behaviour of fascination). The territorial ♂♂ are especially important in this context. Bachelor herds are found predominantly at the periphery of an area inhabited by a gazelle population. Thus predators often encounter them first. Gaits and behaviour patterns in flight are described with special regard to stotting display. The young fawns stay put (Abliegen, WALTHER, 1059/60) and so are difficult to be seen. The way in which the mother manages her fawn especially during the first days of its life lead to the view that the fawn and the place where it rests are kept from contamination with odors attractive to predators. In rare cases even adult gazelles try to evade predators by lying down. Tommies do not fight against predators when hunted. The mother defends her fawn against jackals and tries to divert hyenas which hunt for her fawn. Factors which influence the flight distance are discussed. The flight distance varies with the different predators according to their danger for gazelles. Experiments showed that adult ♂♂ in herds (bachelors) have a lesser flight distance than ♀♀ in herds, adult ♂♂ have a lower one than subadult ♂ ♂, territorial ♂♂ have a lower one than adult bachelors, but solitary wandering ♂♂ show the greatest flight distance of all gazelles. Thus age, sex and social status are all significant factors influencing flight distance. By observations of the behaviour in response to predators, human beings, cars and especially by the study of the mistakes in flights from animals which are not predators of gazelles, it was possible to find a few flight releasing factors, most of them similar to or identical with sign stimuli: sudden appearance, direct course (toward the gazelles), size, good perceptibility (contrast), large number of enemies, high speed, proximity, strangeness, and experience. In concrete cases usually several of these factors operate concomitantly. A remarkable number of them are also known as factors which release the following reaction in young ungulates (WALTHER, 1964a, 1966). This may explain certain cases of ambivalent behaviour, especially of gazelle fawns in regard to predators. A few observations on kills of predators lead me to the view that the age, sex and social groups are preyed upon by various predators at different rates. There are relationships between the differences in flight distances, and the spatial distribution according to the social grouping of gazelles on the one hand, and the different hunting methods of the predators on the other hand. The ecological importance of each predatory species depends on its specialization and preference for gazelles as prey animals, its number, and its preferred biotype. Implications for the management of national parks and game cropping outside the protected areas are discussed. Thomson's gazelles show very few behaviour patterns of alertness, alarm, flight and hiding that are restricted to predators only; most patterns are also seen in intraspecific situations. Certain observations lead to the view that these behaviour patterns are adapted primarily to special conditions of the intraspecific realm and work better in it.
Possible classifications of mimicry - involving model, mimic and dupe - are examined in terms of: mimicry function, nature of the model, mimicry durability and type of species composition. The idea of a three-dimensional classification is developed.-P.J.Jarvis
Two bark-like moth species were tested for resting attitude preferences in an experimental apparatus which allowed a choice between backgrounds having vertically or horizontally oriented surface irregularities. The moths were exposed to either the tactile and visual clues associated with these backgrounds, or to the visual clues alone.When exposed to the tactile and visual stimuli of the backgrounds, a geometrid, with prominent transverse markings, rested at right angles to the surface irregularities (whatever their orientation). Under these same conditions, a noctuid, with prominent longitudinal markings, rested in a head-down attitude, and preferred the vertically oriented surface irregularities.When exposed to only the visual stimuli of these backgrounds, the geometrid exhibited a random distribution of resting attitudes which were unrelated to the background patterns. The noctuid under these conditions maintained its head-down attitude, but lost its preference for the vertically oriented background patterns.On the basis of these results, two mechanisms for effecting an alignment of moth and background patterns are proposed.
The risk (per caput attack rate) of occupying discrete spatial locations within a school of 25 Atlantic silversides, Menidia menidia, under attack by a black seabass, Centropristis striata, was determined. When available, stragglers were attacked more frequently than the school and suffered a significantly higher risk in comparison to school members. Within the school, central silversides suffered the most attacks and sustained a significantly higher percentage of the risk, as compared to peripheral silversides. This finding contradicts theoretical models of the relative benefit of occupying a given location within an animal aggregation and seems to be explicable in terms of predator attack modes and school size.
The electronic version of this book has been prepared by scanning TIFF 600 dpi bitonal images of the pages of the text. Original source: Fascinating mammals : conservation and ecology in the mid-eastern states / Richard H. Yahner.; Yahner, Richard H.; xv, 333 p. : ill., maps ; 25 cm.; Pittsburgh, Pa. :; This electronic text file was created by Optical Character Recognition (OCR). No corrections have been made to the OCR-ed text and no editing has been done to the content of the original document. Encoding has been done through an automated process using the recommendations for Level 2 of the TEI in Libraries Guidelines. Digital page images are linked to the text file.
In nature, the ability to defend against predators is fundamental to an animal's survival. From the giraffes that rely on their spotted coats to blend into the patchy light of their woodland habitats to the South American sea lions that pile themselves in heaps to ward off the killer whales that prey on them in the shallow surf, defense strategies in the animal kingdom are seemingly innumerable. In Antipredator Defenses in Birds and Mammals, Tim Caro ambitiously synthesizes predator defenses in birds and mammals and integrates all functional and evolutionary perspectives on antipredator defenses that have developed over the last century. Structured chronologically along a hypothetical sequence of predationâCaro evokes a gazelle fawn desperate to survive a cheetah attack to illustrate the continuum of the evolution of antipredator defensesâAntipredator Defenses in Birds and Mammals considers the defenses that prey use to avoid detection by predators; the benefits of living in groups; morphological and behavioral defenses in individuals and groups; and, finally, flight and adaptations of last resort. Antipredator Defenses in Birds and Mammals will be of interest to both specialists and general readers interested in ecological issues.
With the color vision and learning abilities of birds and teleosts now proved, it appears possible that the hitherto puzzling massive variation in color and pattern of certain species, distributed through at least five phyla, is not the result of the mere free play of mutation but represents a protective variation and is the product of what may be called reflexive selection.
Alarm calls of Belding's ground squirrels warn relatives, and thus are expressions of nepotism.
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