Transcript predation
動物行為學 (通識) 國立臺南大學 通識課程 2011年春 07 對抗掠食行為 (Antipredator Behavior) 鄭先祐 (Ayo) 教授 國立台南大學 環境與生態學院 生態科學與技術學系 環境生態研究所 + 生態旅遊研究所 Ayo NUTN Web: http://myweb.nutn.edu.tw/~hycheng/ 1 Ayo 2011 動物行為學 (通識) Antipredator behavior Avoiding predators Blending into the environment Being quiet Choosing safe habitats What to do when prey encounter predators Fleeing, approaching predators, feigning death, signaling to predators Fighting back Predation and foraging trade-offs 2 Ayo 2011 Ethology (通識) Snake and ground squirrels Approximately a million years. Strongly selected for ground squirrels to be able to identify their predators and to respond to them with fine-tuned behaviors. Squirrel antipredator behavior includes throwing dirt, pebbles, and roots at putative predators, as well as emitting alarm calls that are specifically made when snakes, but not other predators, are present. and also immunological defenses. 3 Ayo 2011 Ethology (通識) 4 Ayo 2011 Ethology (通識) Ground squirrel pups emerge from their burrows at about forty days. Shortly before this, there is an increase in their immunological defenses against snakes. 5 Ayo 2011 Ethology (通識) Ground squirrel pups often face serious predation threat on their first emergence from their burrow. 6 Ayo 2011 Ethology (通識) Avoiding predators Blending into the environment Cryptic, hidden through camouflaging, making their detection by predators unlikely. 範例：Cuttlefish (烏賊) camouflaging (A) using uniform color to camouflage itself against the rocks (B) using a “mottled (斑駁的) ” camouflage pattern, with small dark splotches resembling the dark patches or rocks and sand (C) a “disruptive(破裂的)” camouflage pattern 7 Ayo 2011 Ethology (通識) Uniform color to camouflage Mottled camouflage pattern Disruptive camouflage pattern 8 Ayo 2011 Ethology (通識) Being quiet Gulf toadfish (prey)and bottlenose dolphins (predator) Dolphins orient toward the “boatwhistle” sound produced by male toadfish during breeding season. Dolphins produce two kinds of sounds, high-frequency whistle for social communication, low-frequency “pops” for foraging. Gulf toadfish become silent. Playback test 9 Ayo 2011 Ethology (通識) 10 Ayo 2011 Ethology (通識) Wax moth and bat Subtle differences between male moth sounds and bat echolocating sounds. Females were indeed able to distinguish between these types of calls and responded appropriately. (playback test) Fanning their wings when they heard male calls But dramatically decreasing this behavior when they heard bat echolocation calls. 11 Ayo 2011 Ethology (通識) 12 Ayo 2011 Ethology (通識) Choosing safe habits Predation and choice of nesting sites in parrots Phylogenies examination showed the ancestral state was tree cavity nesting. Why the nesting in other cavities had evolved independently many time in both Australian and Amazonian parrot species? Whether predation was the key selecting for the shift away from tree cavity nesting? The data on both Amazonian and Australian parrot species do. 13 Ayo 2011 Ethology (通識) encounter with a predator. A scavenging skua gull descends from the air in search of penguin eggs or unattended chicks, while these two gentoo penguins attempt to fend it off. 14 Ayo 2011 Ethology (通識) What to do when prey encounter predators? 1. 2. 3. 4. 5. 15 Fleeing Approaching predators Feigning death Signaling to predators Fighting back Ayo 2011 Ethology (通識) Fleeing The most common response of prey that have spotted a predator is to flee for safety. Flight initiation distance, how close a predator can approach before prey flee. Gathered published data from 61 studies of flight initiation in mammals, fish, birds, and reptiles. (metaanalysis) Animals far from of their refuge initiated fleeing from a predator sooner than animals closer to their refuge. Animals involved in foraging, mating, or fighting were slower to flee from predators than animals were not currently involved in such behaviors 16 Ayo 2011 Ethology (通識) 17 Ayo 2011 Ethology (通識) predators that feed on treefrog eggs (A) here a wasp forages on treefrog eggs (B) Snakes are another dangerous predator on redeyed treefrog eggs. 18 Ayo 2011 Ethology (通識) Treefrogs respond to wasp predation by hatching early. Green bar represent hatching rate of clutches that suffered wasp predation, while orange bars indicate undisturbed clutches. 19 Ayo 2011 Ethology (通識) five days old six days old undisturbed by predation Treefrogs also respond to snake predation by hatching earlier than normal. 20 Ayo 2011 Ethology (通識) Proximate cues? Vibrational cues associated with snake attacks as the proximate cue for when to switch from terrestrial habitats to aquatic ones. To test the hypothesis, using three kinds of sounds (playback test) Two kinds of the vibrations associated with snake attacks and One kind of rainfall The cues associated with snakes resulted in treefrogs that hatched earlier. 21 Ayo 2011 Ethology (通識) Snake attack and eats an entire clutch of eggs A rainstorm Snake eats one or two eggs in s short series of bites 22 Ayo 2011 Ethology (通識) Approaching predators This approach behavior allows prey to gather important information about putative predators and hence reduces their chances of mortality. Approach behavior is often undertaken by healthy adults. This type of behavior has been extensively documented in vertebrates, particularly in fish, birds, and mammals. Prey typically approach a potential predator from a distance in a tentative(嘗試的), jerky(急動的) manner. 23 Ayo 2011 Ethology (通識) 案例：Gazelle antipredator behavior. (A) Gazelles are constantly vigilant (警戒的) for potential predators (B) many different species, including the cheetah hunt gazelles. 24 Ayo 2011 Ethology (通識) 25 (A) the probability of approach behavior occurring in gazelles is a function of group size, as indicated by the logistic curve. Ayo 2011 Ethology (通識) (B) cheetahs respond to gazelle approach behavior. The distance a cheetah move away in response to gazelle approach behavior is also a function of the gazelles’ group size. 26 Ayo 2011 Ethology (通識) Inter-populational differences in approach behavior in minnows Two different populations of minnows (from the Dorset area and Gwynedd area) Dorset population is under strong predation pressure from pike predators While pike are absent from the Gwynedd population of minnows Both populations of minnows increased their group size when faced with predators in the laboratory, but the Dorset population tended to maintain larger groups. 27 Ayo 2011 Ethology (通識) 28 Ayo 2011 Ethology (通識) (A) Dorset minnow respond to predators by decreasing their predator inspection behavior 29 Ayo 2011 Ethology (通識) (B) No statistically significant decrease in inspections occurs in the Gwynedd minnow population. 30 Ayo 2011 Ethology (通識) 31 Ayo 2011 Ethology (通識) Feigning death Faking, or feigning, death is an antipredator behavior seen across a spectrum of species. Adzuki bean beetle Either fly away or feign death Hypothesized that a negative genetic correlation existed between the intensity of death feigning and the ability to fly Artificial selection, longer duration of feign death vs. shortest duration of feign death After 8 generations 32 Ayo 2011 Ethology (通識) 33 The long duration lines are in green and the short duration lines are in orange. Ayo 2011 Ethology (通識) 34 Ayo 2011 Ethology (通識) 35 Ayo 2011 Ethology (通識) 36 Ayo 2011 Ethology (通識) Signaling to predators Warning coloration in monarch butterflies Monarch butterflies ingest milkweed plants, which contain chemicals called cardiac glycosides. These chemicals, which are toxic to birds, do not harm the monarchs. 37 Ayo 2011 Ethology (通識) When a naïve predator eats a monarch, the toxins in the butterfly make the predator violently ill- temporarily . The color patterns of monarchs act as warning coloration for that predator who now avoids feeding upon monarchs. 38 Ayo 2011 Ethology (通識) Tail flagging as a signal Some animals send signals that may serve to notify a predator that is has been spotted. When the predator is an ambush hunter that relies on surprise, such a signal often cause it to move on the leave the area, and hence clearly benefits the prey. Tail raising event in White-tailed deer. 39 Ayo 2011 Ethology (通識) 40 Ayo 2011 Ethology (通識) Fighting back Chemical defense in beetles bombardier defense. When the bombardier beetle is threatened, it releases chemicals that ward off predators. This bombardier beetle is being attacked from the front, and so it is directing its chemical spray forward. They fire the spray backward, when attacked from the rear. 41 Ayo 2011 Ethology (通識) Social learning and mobbing in blackbirds Blackbirds undertake a form of attack called predator mobbing. Once a flock of blackbirds spots a predator, they join together, fly toward the danger, and aggressively attempt to chase it away. Such group attacks often work well enough to force predators to leave the blackbirds’ area. Mobbing is a form of cultural transmission. Animals Raised in captivity failed to have mobbing behavior. 42 Ayo 2011 Ethology (通識) foraging-predation trade-off. When animals are being vigilant for predators, it is often at the cost of other activities. The starlings here can’t be foraging for insects while they scan the sky of hawks. 43 Ayo 2011 Ethology (通識) Predation and foraging trade-offs Squirrels alter their foraging choices as a result of predation pressure from redtailed hawks. Squirrels who could either eat their food items where they found such items or carry the food to cover were more likely to carry items to an area of safe cover, particularly as the distance to safe cover decreased. The closer the refuge from predation, the more likely they would use such a shelter when foraging. Squirrels were much more likely to carry larger items to safe areas before continuing to forage. 44 Ayo 2011 Ethology (通識) (A)Here a squirrel is foraging at a feeding station (B) A squirrel heads for cover with a food item (a part of a cookie) in its mouth. 45 Ayo 2011 Ethology (通識) 動物行為學 (通識) 問題與討論 國立臺南大學 通識課程 2011年春 Ayo NUTN website: http://myweb.nutn.edu.tw/~hycheng/ 46 Ayo 2011 動物行為學 (通識)