After watching Our Planet II, a documentary on the natural world that was recently released on Netflix, a particular scene struck me, discussing the life of ancient murrelets that are hatched on a remote island off British Columbia. What particularly fascinated me was the fact that the moment the chicks hatched, they all started moving in the same direction, towards a river which led to the open ocean, and where their parents awaited them. Although the chicks hatched alone without their parents, each knew in which direction to run, as well as being able to identify their parent.
A similar situation presented itself in a different episode, set on Laysan island, where Laysan albatross chicks, upon being hatched, wait for several weeks for their parents to give them their first and only meal that they did not catch themselves. Once again, the chick knew to stay in the same area, waiting for the parent to arrive and provide food. This may be due to the fact that, without any food being caught for it, the chick simply would not have the energy to attempt to fly out of the island, thus staying in the same place being its only option. However, the same principle applies, where the Laysan albatross parent is immediately aware of which chick is its, feeding it so it has a better chance of survival and, thus a greater chance of offspring and carrying on genes. How are parents and chicks, and generally animals, able to identify themselves with such ease? This is the topic that we will explore in this post.
There is an argument that just as humans can identify each other due to differences in appearance, the same applies to other organisms, just it is harder for humans to spot this difference in other organisms, such as frogs or honeybees. However, the fact remains that as a species, Homo sapiens are vastly different in terms of phenotypes (as well as the remainder of the primate order, eg chimpanzees and gorillas), whereas the organisms mentioned above are more similar. For example, each honeybee in a hive (60,000 in peak months) could not be separated in terms of appearance, although certain castes, such as queen bees, foragers, and drones can be distinguished due to clear differences in morphologies (although surprisingly enough they are genetically identical).
After reading articles on the distinguishing of animals of the same species, it is clear that there is no one form of identification that all animals adhere to. Most animals rely on sight or smell (in the form of chemical cues, odours, and pheromones), whereas others (mainly birds) rely on sound. An example of this is the bottlenose dolphin which produces signature whistles, each characteristic of a particular individual. Research on elephant behaviour suggests that they are multimodal communicators, using 'the complement of visual acoustic, olfactory and tactile information in their social interactions with other elephants'. Furthermore, research has shown that individual honeybees are not able to identify each other, but can only recognise whether or not an individual belongs to the same colony, through pheromones released, with one pheromone specific to each colony.
However, most forms of identification are based on memory/learning methods, which rely on seeing the organism that is family before. In the cases described in the paragraphs above, both chicks hatched with neither parent being present, however, were both able to identify their respective parents. Once again, there is no special answer to this question. Birds often rely on their chicks remaining in the same place they left them (even if they have not hatched yet), and otherwise will not be able to recognise them - therefore the Laysan albatross chicks remaining in the same place that their egg was is crucial. For the ancient murrelet, it is thought that the frequency/sound of the calls/sounds they produce is unique to each animal, with the genotype heavily affecting the noise they produce. Therefore it could be possible that the parents can recognise their young as they resemble themselves, however this is not completely foolproof given the genetic differences that remain between a parent and offspring.
In conclusion, animals identify themselves through a variety of different methods, none of which is 100% foolproof. In certain species, the need to recognise members of a family (i.e. mothers, siblings, young) is extremely important, as this can be used as a basis for nepotism, where individuals will put themselves at risk to defend their family, or neighbours, or form alliances. This is evidently less important in other species of animals, where groups consist of greater numbers of often all siblings e.g. honeybee colonies, and thus it is less important to recognise each individual as an individual rather than belonging to a greater community
Thank you for taking the time to read this post, and keep posted for the next!
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