Interspecific Aggressive Responses

Interspecific Aggressive Responses Competition for food This occurs when resources become scarce. It leads to stress and a reduction in population size, especially for the least successful species. One population may even become extinct. Gause’s Principle (competitive exclusion principle) – ‘no 2 species with identical ecological niches can co-exist for long in the same place’.

Interspecific Aggressive Responses One species will die out, or move away, or the species will differentiate their niches (often subtlety).

Predator-Prey Relationships Not truly an aggressive relationship. Predators can limit a population to a healthy level. Most predators tend to catch the least well-adapted animal, sick or old. Keeps the gene pool of the prey strong. The 2 species are dependent on each others well-being.

Variables in Predator-Prey Relationships The density, size and reproduction rate of the prey animals. The variation in the predator-prey ratios for different prey species. The possible differences in what the predator might eat if there was plenty of food , compared to what it actually does eat.

Factors to Consider… Energy Balance Weather It will not benefit the animal if it uses up more energy in the hunt than it gets eating the carcass. Weather In warm weather, less energy is expended by mammals in keeping warm. E.g. lions need less food than wolves.

Factors to Consider… Size Endurance Larger animals tend to eat less food per unit weight than smaller animals Endurance Cats, in general, lack the endurance of animals such as wolves. They stalk their prey very carefully, saving energy for the short, sharp rush. Wolves always hunt and lions sleep 22hrs a day.

Factors to Consider… Social Systems Size of Prey Male lions may expend no energy on the hunt. These individuals require fewer calories than if they hunted actively. Size of Prey If a group of hunters can bring down a large animal and share the carcass, the energy expended would be worthwhile. Small prey are for individual kills.

Adaptations for Getting Food There are 3 main ways of feeding: Staying in one place and letting the food come to you. Moving about and finding the food. Parasitising another organism.

Letting the Prey Come to the Predator Sifting the Environment Barnacles, mussels, Baleen whales, swifts and some bats Dangle Bait Snapping turtle, angler fish. Both these stratergies require good camouflage to work. Video

Letting the Prey Come to the Predator Webs and Traps spiders Lying in Ambush Praying mantis video

Moving After the Prey Having the Right Appendages Hunting in swarms Army ants Hunting in teams Pelicans, lions, African Wild dogs, Barracuda Using tools Sea otters, Chimpanzees, finches

Parasite/ Host Relationships Parasites, for the most part, exist at the expense of the host. Parasitoids – parasites with a free living stage in their life cycle

Defence Strategies Camouflage Animals can camouflage their smell or the sound that they make. Visual camouflage is the most commonly used means of defence. Bulk is usually disguised by countershading. The silhouette is disguised with disruptive colouration.

Defence Strategies Camouflage Camouflaging eyes is most important as this is the head and brain end, a vital part of the animal. Eyes can disappear amongst stripes and blotches, and some animals flaunt a false eye in a different part of their body.

Defence Strategies Blend and Bluff Certain animals, especially those that are nocturnal, rely on camouflage during the day to go unnoticed. They remain motionless and cryptic colouration protects them.

Defence Strategies Startle the Predator A screech owl bluffs by swelling, and flapping its wings. Many moths have eye patterns on their wings, which they flash. Many caterpillars have eye spots painted on their bodies The caterpillar makes the appropriate part of the body appear thicker, to look like a head.

Defence Strategies Pretend to be Inedible Many animals gain protection by imitating both the physical structure and behaviour of objects regarded as inedible by the predator. A caterpillar or a stick insect looks like a stick and freezes motionless Tropical katydids look like leaves, complete with veins and blemishes A tropical frog sits on leaves and is coloured to look like bird dropping Moths look like tree bark Angler fish and turtles look like rocks

Defence Strategies Mimicry An organism’s close imitation of the appearance of another organism to which it is not related. Batesian Mimicry This is the resemblance of a harmless or palatable species to one that is dangerous, poisonous or revolting. E.g. a fly looking like a bee

Mimicry Mullerian Mimicry Several poisonous species that all have similar warning colouration, this works to the advantage of all the species. Yellow and black stripes are a definite warning and many animals use these colours.

Aggressive Mimicry Amongst cleaner fish. Wrasse, this fish has white and black stripes running along the body. They set up cleaning stations in coral reefs. Fish, recognising their colouration, will queue to be cleaned of parasites. Another fish called a sabre-toothed blenny that mimics the cleaner fish colouration.

Aggressive Mimicry As the trusting fish approach them, they take a quick bite out of a fin or tail.

Warning Colouration – Aposematic Colouration Many animals warn that they are dangerous by having bright colours, especially stripes E.g. monarch butterflies, wasps, striped snakes.

Warning Sounds – aposematic sound Bats hunt at night using ultrasonic squeaks. Some prey moths give out ultrasonic clicks when they hear the bat’s squeaks. The bats never eat these moths.

Firing Chemicals Snakes spit venom. Skunks spray nasty smells. The bombardier beetle fires a revolting chemical in the face of a would be attacker.

Curling up Armadillo, porcupines, hedgehog and slaters all roll up into a ball when attacked. These animals are usually covered with tough scales or sharp spines that the predator can not penetrate.

Retreating Into a Shell Snails pull into their shells, blowing bubbles of a nasty green chemical as they do so. Clams, pipi and toheroa clam up. Turtles and tortoises can pull their legs and heads into their shells for protection.

Keeping Watch Many animals sniff the air and keep a wary eye while they eat. In groups some animals are the ‘lookouts’, allowing others to eat in peace. In mixed groups of animals, the cries of warning by one species will be heeded by others.

Hiding Animals will dive into the mud, sand, snow or anything that will ‘give’ enough to hide a body; then, a quick flick with a flipper, fin or leg covers the back. E.g. flounder

Playing Dead Many predators are geared to only attack live prey, and leave anything that looks dead alone. European grass snake turns upside-down with its mouth open wide and keeps totally still. It also secretes a chemical that attracts blowflies. American oppossums.

Escape by Numbers Offering a predator so many food items at once that it can’t eat them all. Shoaling fish

Interspecific Co-operative Behaviour

Interspecific Co-operative Behaviour Mutualism Both animals benefit Commensalism One animal benefits, and the other is not harmed of benefitted