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– 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– 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–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