When you hear the word 'shark', the image that comes to mind is probably a very archetypal animal; grey, with a slender body, several fins sticking out, a tail at one end and teeth at the other. I call these 'James Bond sharks'. However, there is an incredible array of diversity of different body forms within the sharks and there are some species which look absolutely nothing like the stereotypical James Bond sharks... Allow me to introduce to a little-known group of sharks called the wobbegongs (Family Orectolobidae).
What is a Wobbegong?
There are 12 species of wobbegong, all a part of a family of sharks called the Orectolobidae.
This means, despite looking a little bit like a ray, they are quite closely related to whale sharks (Rhincodon typus) and zebra sharks (Stegostoma fasciatum) (Corrigan & Beheregaray, 2009). To learn more about sharks that look more like rays and rays that look like sharks, you can check out Kissing Cousins.
Wobbegongs are very different in appearance to other sharks, as their head is somewhat flattened and their dorsal fin is positioned far down their back, towards their tail. Also, they have bizarre tassel-like projections around their face, known as "dermal lobes", which inspired their name:
Wobbegong = "shaggy beard"
Wobbegongs Are Ambush Predators
Wobbegongs are "benthic", meaning they spend a lot of their time on or near to the bottom of the ocean. Their body shape and the growths around their mouths help to camouflage them against the rocks and corals of the substrate. This allows them to hide from predators and also to ambush their own prey more easily. Wobbegongs feed mainly on small crustaceans, fish and octopi (Compagno, 1984).
The colour of their skin is also very important for camouflage. Like their relatives, wobbegongs all have very intricate pigmentation patterns, which has given this group their nickname: carpet sharks. As each different wobbegong species has its own unique pattern, with a keen eye, you can learn to tell them apart (Ebert et al, 2015).
Each Species of Wobbegong is Unique
The smallest species of wobbegong is the dwarf spotted wobbegong (O. parvimaculatus), which only reaches a maximum size of 88.5 cm. The largest are the spotted (O. maculatus) and banded wobbegongs (O. halei), which can reach 3 metres in length from snout to tail (Compagno, 1984; Ebert et al, 2015).
These sharks are not generally a threat to humans, but they can give a nasty nip if they are disturbed. Incidents involving wobbegongs, usually involve a person accidentally stepping on one that was well camouflaged on the bottom (Compagno, 1984; Ebert et al, 2015).
Wobbegongs Have a Limited Distribution in the Tropics
Wobbegongs have a very limited distribution. They can only be found in temperate and tropical coastal regions in the Pacific and east Indian Oceans: in Japan, and around Indonesia and Australia (Compagno, 1984; Ebert et al, 2015).
Each species of wobbegong has a different movement pattern within their range. For example, it is thought that ornate wobbegongs (O. ornatus) are not a permanent residents in any particular area, but that they have "short-term site fidelity" at particular locations, and move between these throughout the year (Carraro & Gladstone, 2006).
Comparatively, the Gulf wobbegong (O. halei) exhibits quite long-term site fidelity; with some individuals living within one particular region for more than a year at a time (Huveneers et al, 2006).
These contradicting patterns in movement ecology can make conservation challenging for wobbegongs, as a one-size-fits-all-strategy simply will not work. Creating marine protected areas which will benefit one species of wobbegong, will probably not benefit another, even within the same range, as they might move in and out of these sanctuaries and be exposed to different threats. Due to their coastal distribution and shallow water habitat, wobbegongs are at risk from human disturbance and extraction in fisheries (Carraro & Gladstone, 2006).
Wobbegong Populations are Declining
Whilst on a global scale, none of the twelve species of wobbegong are considered endangered by the International Union for the Conservation of Nature (IUCN), many species are experiencing precipitous declines. For example, the IUCN considers the Japanese wobbegong (O. japonicas) to be declining in the wild. Also, fisheries catches of wobbegongs in Australia declined by as much as 60% between 1990 and 2000. Therefore, there is a very real risk that wobbegongs might be declining (Carraro & Gladstone, 2006).
The problem is that we simply do not know! There are still enormous gaps in our knowledge about wobbegongs and the majority of their stocks have not been assessed - the IUCN reports that it is 'unknown' whether populations are declining for nine of the 12 wobbegong species!
If we are to ensure that wobbegongs stay off of the IUCN Red List of Threatened Species, it will be vital to learn as much as we can about their ecology as soon as possible. We must devote more effort to assessing all the different species of wobbegongs and implementing management strategies... It is far better to implement measures to ensure a species does not decline in the wild, than it is to try to repair the damage after a population is pushed to the brink of extinction!
Because, let's be honest, we want these bizarre and beautiful animals in our oceans for everyone to enjoy for many generations to come!
References
Carraro R & Gladstone W (2006). Habitat preferences and site fidelity of the ornate wobbegong shark (Orectolobus ornatus) on rocky reefs of New South Wales. Pacific Science, 60:2, 207–223. Access online.
Compagno LJV (1984). Sharks of the World: An annotated and illustrated catalogue of Shark Species Known to Date, Volume 2: Bullhead, mackerel and carpet sharks (Heterodontformes, Lamniformes and Orectolobiformes). FAO Species Catalogue, Rome. Access online.
Corrigan S & Beheregaray LB (2009). A recent shark radiation: Molecular phylogeny, biogeography and speciation of wobbegong sharks (family: Orectolobidae). Molecular Phylogenetics and Evolution, 52, 205–216. Access online.
Ebert DA, Fowler S & Dando M (2015). A Pocket Guide to Sharks of the World. Princeton Books. ISBN 978-0-691-16599-8.
Huveneers C, Harcourt RG & Otway NM (2006). Observation of localised movements and residence times of the wobbegong shark Orectolobus halei at Fish Rock, NSW, Australia. Cybium, 30:4, 103-111. Access online.
By Sophie A. Maycock for SharkSpeak
