For years, human youth constantly tell their parents "I do not want to be like you". But for all animals, this is not the case.

Some spend their juvenile stages looking and acting very differently when compared to their parents. However, as they progress towards adulthood, become similar or exactly like their parents. The goal of this week's article is to highlight some species found on our planet where the juvenile stages vary from the adults. In some species, so much so that they are mistaken for different species. I will also highlight why this difference between the life stages of a species is important to its survival.

The best way to see how juveniles differ from their parents is through examples. But before going into that, one has to understand the importance of why in some species it is beneficial for the different life stages to differ from each other. In order to understand this, one needs to understand about the basic requirements organisms need to survive and the niches they occupy. In order for a species to survive in an area or region, members require some basic resources, namely water, food, space and an adequate supply of mates. However, the latter requirement is only necessary to individuals of reproductive age. This leads one to question how so many species co-exist in an area without depleting the resources found there. The answer to this is that, species occupy different ecological niches. A niche can be defined as "the ecological role and space that an organism fills in an ecosystem". This is also the reason why in some species, many individuals can occupy the same area.

The most obvious difference between juveniles and adult members of most species is their size. However, this is not always the case and in some species the juveniles differ so much from their parents in appearance that they are mistaken for new species.

This has been the case of species of dinosaurs which have gone extinct so that one has to go on the appearance of the fossils they have left behind rather than using DNA analysis. In the sea bird species (as on Little Tobago), the brown booby juvenile is covered in a white fuzz and is 3-4 times larger than the parent/adult.

Juveniles differ from their parents not only in appearance, but where they live. For instance, mangrove swamps act as nurseries for many species of fish and crustaceans.

Which go on to lead their adult lives in the ocean. Another example, are Leatherback turtles (Dermochelys coriacea) which spend their entire lives in the ocean only coming onto beaches to lay their eggs, so that their eggs and hatchlings spend about two months in a terrestrial environment.

Therefore when it is turtle nesting season, it is important not to disturb (as we commonly do in T&T) the beach by driving vehicles or by having large parties on the beach that will act to compress the sand so tightly that the eggs might get crushed or the hatchlings cannot emerge.

Our shores are home to other sea turtle species, Green turtles (Chelonia mydas). This species provides a perfect marine example of how juveniles differ from adults when it comes to diet and niche occupation. Hatchlings and juveniles (that is, individuals up to five years old) are found in the shallow waters in the convergence zones within the open ocean. However, pregnant females will come ashore to lay their eggs. Therefore they occupy different microhabitats. Even their diet also prevents competition between individuals at different life stages. For instance, hatchings are carnivores while juveniles and adults are grazers (herbivores). Since hatchlings do not have to compete with their own species for food they stand a greater chance of survival.

By acting as carnivores rather than herbivores like adults, they are not competing for food with the adults. This also applies to plants as well, for instance the sapling of some species are adapted to living in the shady conditions of the understory layer of forests rather than competing with adults to become part of the canopy. Some saplings can spend their entire life in the understory level only becoming part of the canopy if there is a tree fall. The saplings do not compete with the adults for space, or light, but rather replace the adults when they die.

In addition to changes in habitat between the juveniles and their parent, in some marine species, the juveniles are mobile while the adults are either less mobile or stationary, an example of this are sea urchins. Adult sea urchins spend almost all of their lives relatively stationary with respect to their physical location. The juveniles on the other hand are quire mobile. The larva is free-moving and when it is time to develop into an adult the larva sinks down to the substrate.

In closing I would like to highlight that when it comes to conservation, much emphasis is placed on the existence of adult individuals of a species, in most cases because they are of reproductive age.

However, in some species, the juveniles occupy a completely different ecological niche, sometimes in a different habitat or another part of the world. Therefore the areas regarded for conservation have to be greatly expanded simply because juveniles will themselves become adults and continue the lifecycle and existence of the species.