BIOL1007 Lecture 23 – Individuals, behaviour & environment Understand links between morphology, physiology, and behaviour Behaviour o part of how organisms respond to the environment e.g., biotic and abiotic environment abiotic environment o e.g., lizard moving of legs on hot Namib desert sand is an example of how animal behave to keep its temperature within bounds in relation to the physical environment biotic environment o essentially a kind of coping mechanism o 3 behavioural aspects obtain food avoid being food reproduce Links between morphology, physiology, and behaviour o Behaviour does not act on its own, it works with morphology and physiology o The physiological and morphological constraint associated with the organism that you are dictate in some ways of the animals’ behaviour. o e.g., Gelada baboon The only grass feeding specialist monkeys in the world Morphology dental morphology suggesting that they are able to grind up grass gut Physiology capacity to digest plant cell wall in grass Social behaviour group size, conflict between feeding, safety, mates Appreciate ecological & evolutionary significance of behaviour How can behaviour affect fitness? o Fitness = an individual’s relative contribution to the next generation’s gene pool o Behaviour can influence the number of offspring that an organism can produce, which means it has a direct effect on an organism’s fitness o Example using plant-insect interactions Insect herbivores consume vegetative parts of plants (e.g., leaves) Insects pollinate around 2/3 of all plnats; often with food rewards(e.g., nectar).
o Do food quality affect butterfly reproductive success? It was expected that if the larvae of the butterflies or the adults are provided with very high quality food, they should reproduce younger, and that will in turn provide a fitness advantage for them. o Does foraging on high quality food provide a fitness advantage? In the experiment, the larvae were first given fertilisers with greater or lesser amount for the larvae (with grass). After they turn into adults, for both cases for the larvae that werefed on low fertiliser grass that are provided with foods that was low in amino acids, or high in amino acids. The results showed that feeding on high quality food increases the reproductive output (which is used as a surrogate measure of fitness) Therefore, the foraging on high quality food did provide a fitness advantage. Behaviour is ecologically significant because o a link between individuals and how they cope their environment o affects demographic (population levels outcomes) o affects interactions among species (community-level outcomes) Behaviour is evolutionary significant because it o have some genetic basis (think nature vs nurture) o affects fitness – the numbers of young that were produced o can be selected (benefits > costs) How do we know? o Observations: inter- and intra-specific comparisons o Manipulative experiments that test hypothesis Understand various behavioural strategies to obtain food and avoid being food Behavioural strategies to obtain food o Foraging strategies are linked with morphology and physiology e.g., ambush predator : camouflage, lies in wait increase probability prey encounter e.g., ant-lion, Peringuey’s adder e.g., active predators : agile, fast increase probability prey encounter e.g., dingo, cheetah o Huge variety of foraging strategies , defined by What they eat frugivore, herbivore, nectarivore, granivore, graminivore, insectivore, carnivore, omnivore o frugivore = animals that thrive entirely or predominantly on fruits or fruit-like vegetables o herbivore = organism that feed mostly on plants o nectivore = animal that principally eats nectar
o granivore = animals that feed on seeds of grass o graminivore = animal that feeds primarily on grass o insectivore = animal that feeds on insects, worms, and other invertebrates o carnivore = organism that mostly eats meat, or the flesh of animals o omnivore = animal that has the ability to eat and survive on both plant and animal matter How they get it ambush vs active Diet breath specialist generalist o specialist = more specialised in what they eat, e.g.,koalas only eat leaves and eucalyptus o generalist = eat a wider variety of food, e.g., squirrels o Common feature of all foraging strategies non-random, i.e., individuals make foraging choices o How do they choose where to forage and what to eat? Optimal foraging theory modelled which food items to eat in a non-depleting environment simply an idea that animals will find sitting in patches where food is most abundant, most available, and eat it predicts foragers should maximise net rate of food (=energy intake) kind of unrealistic, because this theory imagined that the animals are eating in a non-depleting environment focuses on efficiency of energy gain Marginal value theorem (1970s) modelled when to leave food patch in a depleting environment predicts that foragers should leave food patches when capture/harvest rate at patch < average capture/harvest rate o In other words, the food patch is no longer differentfrom the rest of the surrounding environment. If that’s the case, the animal should leave and find somewhere to forage. Foraging ecology tests predictions about foraging behaviour o We should therefore expect: foraging strategies to be linked to predator avoidance strategies remember that most foragers are also prey
a trade-off between food and fear Behavioural strategies to avoid being food o The dead don’t reproduce o Being eaten: ultimate fitness cost o develop strategies to decrease predator risk For anti-predator strategies to evolve, just need benefits > costs o relevant to most of food chain If the animals are below the top predator (see the above diagram), it should be something that they are worrying about. o Anti-predator strategies include Run away Group together Hide e.g., crypsis = any adaptations that causes an animal to be less conspicuous (e.g., visually or chemically) to the predators Act costly act dangerous, mimic unpalatable or toxic organisms Be costly e.g., sequester toxic compounds – ants secreting formic acid that will put off a potential predator e.g., have spines – porcupine spines Feed in safe places or times e.g., vegetation cover, new moon e.g., red-bellied pademelons are more likely to feed closer to shelter o The cover provides these animals with protection. The further away they move from it, the more scared they feel. o But there can still be costs to anti-predator strategies: feeding near vegetation cover missed opportunities to forage somewhere? group competition for food, social aggression? The bigger the group, the more competition there could be for food. The smaller group on the other hand, the greater the risk of being spotted and taken by predators. Understand strategies used in reproductive behaviour Behaviour to reproduce
o Courtship and mating behaviour: non-random relevant to sexual reproduction involves male-male competition female choice results in non-random mating (& non-random offspring) Darwin suggested important concept: sexual selection (2 types) intrasexual selection competition (often male-male) sexual dimorphism (e.g., hefty vs slight) intrasexual selection mate choice (often female) sexual dimorphism (e.g., flashy vs plain tail feathers) o Parental care Why bother? For parental care to evolve: benefits > costs o Benefits: increased survival and growth of offspring (= fitness) o Costs: missed opportunities (to reproduce again) Parental care & cooperative breeding In some species, offspring stay and help parents rear more offspring Is having the kids around worth it for the parents to rear more offspirng? o Test: 19-year study of the superb fairy wren ( Malurus cyaneus ) o Result: increase number of independent young with more helpers to rear more offspring. o The independent young are also learning how to rear offspring. o Conclusion: For the Malurus cyaneus YES! o Trade-off costs vs benefits How could the male peacock’s tail possibly arise from natural selection? High costs of such a tail (thinking energy in production & maintenance; risk of predation) Benefits : access to mates (female behaviour certainly drives the elaboration of the tail feathers in male peacocks) Darwin hypothesised the female peacock tail arises from natural selection, via selective pressure associated with sexual reproduction. Understand whether behaviour is something only animals do Examples of foraging behaviour
o They have to use behaviour to negotiate both of these things, that is finding appropriate food, and avoid being eaten while they do so. o Do organisms need to have a brain to be able to behave? not necessarily (note the example for slim mould from the table, and plants) No, other organisms have behaviours as well. o Plant behaviour different time frame (plants move slowly) different way of moving (plants move parts of themselves (modular)) Similar: all living organisms respond to their environment o Leaves and stems grow towards light respond to their environment by moving o Roots grow along chemical gradients towards nutrients respond to their environment by moving Appreciate the science behind our knowledge and understanding of behaviour So, what is behaviour? o Interaction with environment (abiotic and biotic) o Involves stimulus: response The response to stimuli might be food, if the animals arefeeling hungry, they need to move to a patch with more food. o Involves sensory Sensors that can detect where these aspects of the environmentwill be located We can draw parallels between animals (classic behaviour) and other organisms to understand general principles of how individuals interact with their environment.