In the wild, diverse groups of organisms constantly evolve different adaptive qualities to get an edge over other organisms in their survival and maintaining their gene pool. Some small organisms get eaten by other large carnivores. The hunting species is called a predator, while the species being hunted is a prey. The prey animals are constantly evolving themselves to defend themselves from the predator, and thus, prey animals come with better defending strategies. Predators also need to acquire food, so they evolve to combat these defending strategies. Some of the strategies used by prey animals to safeguard them are crypsis, aposematism, mimicry, camouflage, and many others.
Let’s have a look at some of the aforementioned defence strategies-
Crypsis- This strategy involves hiding away from the predator. It can involve auditory, visual, and olfactory concealment. One of the most commonly known methods under crypsis is camouflage. Camouflage refers to changing the body colour to that of the environment and becoming invisible. Octopuses and chameleons are famous examples of camouflaging organisms. In octopuses, the camouflage happens in a blink of an eye because they are controlled by photoreceptor cells, while in chameleon, it takes a few seconds to achieve this because the colour change is controlled by hormonal levels. Though crypsis provides protection from predation, it limits the opportunity of organisms showing crypsis to explore their environment and move around freely. During foraging, they pose a risk of being hunted. Due to this factor, aposematism is considered better compared to crypsis.
Aposematism- it is the strategy adopted by few organisms in the wild to avoid predation, in which the organisms pass certain warning displays to the predators to alert them of the danger present in eating them. Aposematism is basically an advertisement to potential predators that they are not worth eating. They can advertise by having their body colour in contrast to the background, having spikes on their body, or releasing noxious odours. Some organisms, having an attractive body colour like ladybirds, release bitter-tasting chemicals which would give a bad experience to the predator after eating it, and thus the predator will learn to avoid the next time they encounter such a coloured beetle.
Aposematism consists of two elements-
Primary defence- it includes warning the predator by showing external body features or releasing smell.
Secondary defence- this defence comes into the act when the predator ignores the primary defence and comes to attack the prey. These may include chemical and behavioural strategies.
Organisms showing aposematism are somewhat sluggish, moving slowly as they do not spend much of their energy in movement; instead, they use that energy to defend themselves.
Aposematism can sometimes be disadvantageous in terms of attracting mates. For example, the wood tiger moth has two colour polymorphs, one yellow coloured male and the other white coloured male. The yellow coloured male, which shows aposematism, is better protected from predation while the white coloured male is better at attracting females for mating.
The success of aposematism also depends on the predators. If a new bright coloured species emerges, the predators tend to avoid it because of neophobia (avoiding new food because they are scared to try it) and diet conservatism (resistance to changes in diet). This will lead to the thriving of the new aposematic species. Also, if the food is scarce, the selection pressure will lead to the evolution of predators, and this can combat the strategy of aposematism. Aposematism usually helps both the predators and prey animals. Prey animals advertise defence using this strategy while the predators benefit with enhanced learning, memory( to remember the warning displays of prey), and their recognising ability. Aposematism can be exploited by other organisms, which can give rise to Müllerian mimicry and Batesian mimicry.
Let’s see the other strategy used by the prey and even predators to enhance their survival:
Mimicry- There are many talented humans who can mimic the voices of other humans and trick others. Similarly, certain organisms use the art of mimicry to trick other organisms and get benefits. Unlike humans, animals mimic the body shape, structure, and colour of other animals(called model animals). The mimic need not be exactly like the model organism but should look similar to some extent (at least 50 %.) Most of the time, 50 % or more resemblance can also benefit the mimicking organism.
The two main types of mimicry are-
Müllerian mimicry- müllerian mimicry refers to the case when an organism of one species mimics (in size, structure, colour) the organism of another species showing aposematism. In this case, both organisms show aposematism and are unpalatable (distasteful, toxic, etc.). In this way, along with the predators learning to stay away from them(which requires the initial killing of certain aposematic organisms to get a bitter experience), a lower number of organisms will be killed from each species. Lycid beetle(model) and arctiid moth(mimic) are müllerian mimics.
Batesian mimicry- This type of mimicry is more of a parasitic mimicry. In this mimicry, an organism mimics just the warning displays of an aposematic organism(model) and does not possess any secondary defence and thus is palatable. These organisms can put the life of the model aposematic organisms in danger because if the predator first encountered the mimic, it wouldn’t get a bitter experience. This can put the model and the predator in danger. That is why the mimics should be rare so that the reputation of an aposematic organism is maintained, and it benefits both the model and mimic.
Some Other types of mimicry-
Aggressive mimicry- this type of mimicry is shown by the predators in which they mimic non-threatening organisms to reach close to their prey and hunt them. In some cases, the predator may even mimic the prey of its intended prey.
Floral mimicry- this mimicry is seen in flowers. The flower gives rewards like nectar to insects in return for pollination. Some flowers which cannot put energy (due to the lack of nutrients) to produce nectar mimic nectar-producing flowers to attract pollinators. Some flowers even mimic the female of an insect. This attracts the male insect, which is actually looking for a mate, towards the female-looking flower but instead of mating, the male ends up pollinating the flower. This phenomenon of mimicking female insects and attracting males is called pseudo-copulation.
Intraspecific sexual mimicry- As the name suggests, this mimicry is related to mimicking of sex in the same species. Usually, the males mimic females to gain an advantage. One example is the male garter snake which produces female-like pheromones and attracts males after emerging from hibernation. This may benefit them because the mating ball formed by the males around it helps to keep away predators, help them to heat up fast and make them more active.
Automimicry- the extent of aposematism in the organisms of the same species also varies. It depends on the availability of proper nutrients and other factors. Certain organisms in the same species lack proper nutrients and could not exhibit aposematism, and thus they mimic their aposematic conspecifics to defend themselves. This type of mimicry occurring within the species is called automimicry.
Conclusion:
Aposematism, crypsis, and mimicry are just a few of the defence strategies adopted by the prey animals to keep themselves safe from large predators. There are countless others. Also, the prey and predator animals are constantly developing new strategies in order to survive in the race of life. Predators and prey animals are involved in a type of arms race. This article mainly focused on one side of the coin that is how prey animals develop strategies to combat predators. But predators also develop new skills against the defending techniques developed by prey animals.
References-
Book name
Avoiding attack: the evolutionary ecology of crypsis, aposematism, and mimicry
By- Graeme D Ruxton, William L Allen, Thomas N Sherratt, Michael P Speed
