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Chapter 5 Primary = Operates whether or not predator is there. – Decreases probability of an encounter with a predator Secondary = Once detected by predator increases probability of surviving encounter Ex. Noctuid moths - A1 receptors = primary; A2 rec. = secondary 1. Crypsis (camoflaging) a. color pattern Body color: Many animals are cryptically colored to blend in with their environment - fawn brown with white spots, make it blend in with patches of sunlight on forest floor Disruption patterns: may break up animal's shape or discernable features ex. stripe across eye of frog Color and body form - mimic leaf, stem, thorn behavior reinforces color pattern 1. animals remain still or may move to mimic object blowing in the wind 2. body orientation: important if color pattern must be aligned with that of background Ex. if mimicing a thorn, thorn must be aligned with others Ex) African cicida moth (Ityraea) mimics a flower, a group clusters on a flower stalk (all oriented the same way) mimicing an inflorescence (group of flowers) Not only is the color pattern, but the behavior is an adaptation Jays trained to peck at Catocala relicta moths for reward 10-20% reduction in “capture rate” if on pale birch bark & positioned with head up. 2. Bluff - look like what you are not a. mimic predator's predator - snake b. something distasteful - bird excrement c. again behavior is important - correct orientation or sway body 3. Aposematism - warning coloration = warning of a distasteful or dangerous quality predators usually have to learn this pattern. Ex. Monarch, coral snake complex = color Ex. wasps and bees - yellow, or orange and black Cost – Benefit analysis can be used to study conspicuous coloration and behavior. Tephritid flies wave conspicuous wings – How is this adaptive? Looks like jumping spider T. flies with clear wings were eaten House flies with T wings were eaten as well Wings & behavior needed 1. Misdirection of attack a. false head- lantern bug - hairstreak butterfly b. Asian web-building spider (Cyclosa) builds a platform where it sits ready to pounce on prey and 2 pseudo-platforms. 2. Distraction hind wings – eyes, bright color hiss - cockroaches 3.Defensive secretions a. ant guards (wasps, bees) Ex. Polistes, Polybia b. sticky solution, (black widow spider, termites) Ex. Nasute termites - heads like guns in soldier caste Ex. black widow spider - eaten by mice - spider if touched, immediately secretes web with sticky droplets on it - smear in face of mouse. The time it takes the mouse to get rid of sticky mess, spider has opportunity to escape c. chemical repellents (Bombardier beetle, sting, poison toads, salamanders etc) Ex. Bombardier beetle - 2 glands combined = explosive reaction burning chemical Ex. Eucalyptus sawfly larvae Ex. Sting – scorpions, bees, ants, etc. 4. Evasive behavior flight or withdrawal - into burrow or other retreat 5. Group defense A. mobbing of predators small birds such as starlings attack larger predatory birds - hawks. Seem to endanger themselves. But seem to so distract and harass predator that it seems an effective way to drive off predator or cause it to miss seeing prey. group attack in stinging insects - more effective too a. sting chemical attracts others to join in attack B. Group position 1. musk oxen - stand in circle; pods- young to center C. Benefit of just being in a group 1. predator can only capture so many - saturate predator - mass emergences of insects - large herds of animals or schooling in fish 2. more eyes 3. better to hide behind someone else - Selfish herd hypothesis (W. D. Hamilton) a. what may look to be a cooperative flock or herd, may really be many selfish individuals - all trying to hide behind someone else 6. Get help from symbiotic relationship with another species - aphid and ants 6. Get help from relationship with another species - aphid and ants (symbiosis) - large and small nesting wasps (commensalism) The goal of most animals is to manage to get enough food to sustain life and reproduce. feeding behavior requires an expenditure of energy (cost) Animals should try to reduce the cost of feeding while trying to maximize the net gain in energy (which can then be put toward reproduction) Net (energy) gain = Food acquired - energy required to get it (benefit) (cost) (in this society, cost is so low, we often have a problem from the net gain in energy which we store as fat) Remember: animals should behave optimally by maximizing gain and minimizing costs Ex. Crow foraging by Reto Zach Crows - seashores eat shellfish Assumption: Crows are foraging optimally so as to maximize benefit while minimizing cost Hypothesis: Benefit = amount of whelks eaten/ time; Cost = energy used to fly to a height for dropping the whelk to break it open Number of Drops per Whelk 100 90 80 70 60 50 40 30 20 10 0 Ht. of Drop (m) Calories gained (benefit) by eating whelks of different sizes could easily be measured. Results: Only large whelks would break open easily enough and provide enough energy (calories) for the crows to gain a net amount of energy. If crows forage optimally Prediction 1: Crows should only feed on large whelks and ignore small ones. Tested by providing crows with a selection and recording which they took. Results: When given a selection, crows ignored all but the largest whelks Prediction 2: crows should choose a dropping height that will minimize the total expenditure of energy. Total Ht./ Whelk (m) Figure below estimates this: at ht of 5 m drop, may have to drop 4 times to open = tot. 20m; at ht of 7 m drop, may have to drop 3 times to open = tot. 21m 120 100 80 60 40 20 0 1 3 5 7 9 Ht. of Drop (m) 11 13 15 Greater the height Whelk may bounce away and be lost Another bird may have time to reach prey first So birds should use the lowest dropping height possible for maximum gain. Looking at previous graph – Zach predicted average height of drop would be around 5.5 m. Total Ht./ Whelk (m) 120 100 80 60 40 20 0 1 3 5 7 9 11 Ht. of Drop (m) Conclusion: The crow does indeed seem to be programmed (genetically predisposed) to choose the size of whelk and the dropping height that maximizes its net energetic profit. Since the crow's behavior fit the predicted pattern, the constraints on the behavior identified by Zach appear to be correct. Factors: 1) size of whelk, 2) energy spent in flight, 3) competition, 4) loss of whelk if dropped from too high 13 15 Similar study Energy model would predict largest mussels would be chosen Not supported Hypothesis: some large mussels can’t be opened, model modified to account for longer average handling time. Prediction – 50 mm average Hypothesis rework: barnacle coverage on largest mussels makes these impossible to open – these should be avoided Model predicts 30-45 mm average Marginal Value Theorem longer in the patch, the less the return in food Net Return Time in Patch When should an animal decide to go to a new patch? depends on time to locate and travel to a new patch optimum time to move is when the max. gain is attained Net Gain A B Time to Move Between Patches 0 B A Time in Patch 1. nutritional constraints on foraging Animals do not just need calories (energy). Variety may be important to get a full range of needed nutrients. Often a particular mineral or amino acid may be in low concentration in normal diet. Animal must make a special effort to feed on a particular food or consume enough of its normal diet to get the limiting mineral or amino acid. 1. Lycosid spiders consume a variety of small prey (not high energy yield). But lycosids on a varied diet reproduce better than those maintained on a diet of a single prey species. (9 essential amino acids can't be synthesized and are needed from diet). 2. Moose - terrestrial plants - high energy but aquatic plants - high sodium (which is limiting) 3. Aphids - feed on plant phloem - high sugar content, but low amino acid content; Aphids must feed a lot; excess sugar given off (why tended by ants) This may force animals to search out and feed only on certain plants and animals that have lower toxin levels Example: Tassel-eared squirrels - feed on bark of ponderosa pines. Variation in amounts of terpenes in trees. Animals may not always appear to be foraging efficiently. There may be trade-offs between the value of a particular foraging method and some other less obvious cost, such as danger from predators Example - Juncos (seed eaters and prey of hawks) while feeding, juncos stop and look about 15X /min Often feed in flocks (increased competition, but more eyes and the less time each must spend looking) - this changes, if a predator is in the area, juncos singly or in flocks will spend more time looking Dugongs feed on sea grass Grazing on grass tops ▪ Good visibility Rooting up the holdfasts (excavation) ▪ Poor visibility ▪ High nutrition Presence of sharks Impacts foraging Example: small bird - good seed patch (might not last), spends some time checking out other seed patches even though good patch is all it needs If animal does not have exclusive access to food patches, the density of competitors might change duration in a patch. May also result in selection favoring territorial behavior and the defense of patchy resources. Herbivory: feed on plants, which = primary level of food production Plant defenses: (when predation not wanted) Mechanical: hairs with hooks, thorns, tough outer coating Chemical: a. reduce digestability Ex. tannins, silica: b. cause nausea or death to those who feed on them Ex. pyrethrin (natural insecticide), cardiac glycosides (milkweed) c. hormones - interfere with insect development and reproduction B. In response, different animal species have evolved ways of getting around specific plant defenses 1. plant mechanical defenses Passiflora adenopoda hooked hairs on leaves - butterfly larvae get hooked and die all except one which specializes on this plant = Mechanitis isthmia – butterfly larvae feed in groups and they spin a web covering over the hairs and feed together on the exposed edges of the leaves. 2. chemical defenses - such food has few competitors => good resource some animals' physiology has evolved to deal with particular plant defenses animal usually becomes a specialist - feeding on only one or 2 plants ex. Monarch butterfly - milkweed (evolved a tolerance for the cardiac glycosides - stores toxins in its own tissues) ex. horses and cows can feed on grass, our teeth would wear down rapidly due to silica in plant tissues Plants may ‘want’ animals to feed on them: For pollination (pollen houses developing male gametes) - transfer of pollen to female organs of another flower. seed dispersal - animal eats fruit, flies and disperses seeds Plant provides nectar to attract pollinators - they will carry the plant's pollen to a neighboring plant - of same species. Plants have evolved structures that ensure that only one or a few species can pollinate them. These animals will in turn tend to specialize. Ex. different types of flower mechanisms Flower structure: Nectar may be down a long tube, which only bees with long tongues can reach Some have nectar sources hidden in capsules that will open only if a sufficiently heavy insect alights upon the flower. Flower color: red – moths and birds; white – nocturnal; UV – bees, wasps Ex. Timing of flower opening Day versus night Ex. Small nectar flow may tend to attract smaller insects 1. 2. Attractive fruits, seeds Various attaching devices As animals feed and move around, they help to disperse the progeny of the plants An entire area of research deals with animalplant interactions. Internal ◦ Modified for entering body – may involve multiple life stages, with only some parasitic ◦ Parasitoids – lay one egg, which multiplies in host ◦ Usually pale and small External ◦ Usually have structures for holding on or moving through hair ◦ Flattened to be against body, small, match host Parasitic is a specialized form of carnivory Predation Chase prey Filter feeding Aggressive mimicry ▪ Preying mantid = flower or leaf ▪ Fishing with lures : Anglerfish • Lightning bug females Photuris female eats males of Photinus spp. Ant lions Bola spider Chimps Archer fish Woodpecker finch Egyptian vulture Sea otters Whales http://www.youtube.com/watch?v=1DoWdH Otlrk David Wiley, Colin Ware, Alessandro Bocconcelli, Danielle Cholewiak, Ari Friedlaender, Michael Thompson & Mason Weinrich •Whales create bubble nets by releasing air while swimming in spirals or circles. •They feed on small fish that school or krill •Feed by opening mouth, taking in a large volume of water and filtering food out of the water as it passes through the baleen •Bubble size varies from Atlantic to Pacific. Feed in clustered groups Some will add bubbles to another’s net Some may feed within another’s net; perhaps in a mutual sharing It is possible that some are stealing from another’s net. Benefits of social prey capture: 1. Flocking birds - more eyes to locate food, transient birds benefit most from knowledge of residents 2. Kill larger and more dangerous prey than could be handled by a single individual 2 different extremes: a. Terrestrial vertebrate carnivores : cats (lions), dogs (Wild dogs, wolves), and hyenas Ex. Lions - females live in small groups and hunt together (occasionally one or two males) Some may act as decoy, others charge from a different directions simultaneously b. Invertebrates: army ants (more details in 3 wks) Ex. African driver ants (colonies 20 million) -swarm foraging Saprophagous and Coprophagous http://www.youtube.com/watch?feature=playe r_embedded&v=q703ArSTDE0 Feed on dead plant and animal tissues or excrement Omnivores