Little known facts about seahorses

I have been reading up about seahorses recently and discovered some interesting little bits of information I could not help but share. While seahorses seem to be a big favourite for divers and non-divers alike, we actually know surprisingly little about them. Some of their strange quirks are well known. The fact that the males get pregnant is probably one of the favourite and most retold bits of knowledge about them. I want to go a bit further and more interesting than that, so let’s get started.


The fused jaw of a seahorse (Source)

Seahorses belong to the family of Sygnathidae, which  translates as “fused jaws”. What this means is that all seahorses and pipefishes have jaws that are stuck together, they can’t open them anymore. So if you were to imagine eating like a seahorse, try gobbling up your salad, steak, pizza, apple,… with clenched jaws, while only using your lips to help you suck the food in. A good thing seahorses do not have teeth, as that would make it even more difficult!

Best of Dauin_Seahorse Estuary_MDB

Hippocampus taenopterus, getting ready to growl

Another quirky thing seahorses do, is that they make noise. They make two distinct types of sounds: “clicking” and “growling”. I absolutely love the idea of a growling seahorse! It seems they do this when they are stressed out and it might even be some sort of escape mechanism to startle predators. Most likely because those predators would be laughing too hard because a seahorse just growled at them… The clicking sounds are mostly used during courtship and mating, so not only do seahorses growl to chase away predators, they also serenade their partners to get them in the right mood. Strange little critters indeed.

To keep up with the strangeness, have you ever wondered how strange the tail of a seahorse actually is? Probably not, I definitely hadn’t before reading this article.  The tails of most animals are round, but nearly all seahorses have square tails. As it turns out, this square shape is better at grasping and holding items. At the same time it offers a higher resistance to crushing than a round tail would. So perfect for a camouflaged critter which spends most of its time clinging on to objects, pretending to be something it is not to avoid getting eaten by predators.

Seahorse tails

Different 3D printed models of seahorse tails (Source)

Best of Dauin_Seahorse thorny_MDB

Hippocampus histrix

The objects seahorses hold onto can be anything, usually they cling on to objects like seagrass, algae, gorgonian seafans, etc. But they do not seem to be very picky at all. This article showed how seahorses living in areas with a lot of plastic actually use that plastic as camouflage. The seahorses even changed their colour to resemble the colour of the plastic and the spots on it. Unfortunately I cannot put the original pictures online due to copyright issues, so if you want to see them, follow this link. Since seahorses don’t really mind what they hold on to, artificial structures can be used to provide habitat for them when their natural habitat has been destroyed. This way populations can continue to exist until the natural vegetation has recovered.

Loss of habitat is one of the risks that endanger seahorses, the trade for traditional Chinese medicine is another big threat to them. IUCN has listed 7 species as Vulnerable and one species as Endangered, but most species have either not been assessed or we lack the data to assess whether or not they are endangered. To combat the illegal trade and offer some means of protection, all seahorses are listed with CITES, which means trading them is strictly controlled. One of the simple rules used to do this, is a size limit of 10cm. This size ensures that most traded seahorse species are mature individuals who can reproduce and that juveniles are left alone.


Hippocampus pontohi

The fact that we don’t really know how many species of seahorses exist, makes protecting them hard. Estimates of the number of seahorse species range from 40 to 48 species. It is quite likely new species are still waiting to be discovered, though the opposite might happen as well. Two species of pygmy seahorses (Hippocampus severnsi and Hippocampus pontohi) were described in 2008. But recent genetic analyses showed that they are actually the same species which comes in different colour variations.


If you want to know more about seahorses or just have a good laugh, check out this great video from Ze Frank with some more true facts about seahorses.

Explosions of colour in the centre of marine biodiversity


Sea Safari 6

I recently returned from another liveaboard trip, this time in Raja Ampat. I’m writing this blog in Sorong, after just having disembarked from the Sea Safari 6. We spent 10 days diving both the south and north of Raja and it was pretty spectacular. I was lucky enough that Safari Bali saved me a free spot on the boat again, allowing me to do research. The only thing I had to do in return, was talk about fish, since I do that all the time anyway, I consider this to be a pretty sweet deal.

The Raja Ampat region is found in the east of Indonesia, in the province of West Papua. The name “Raja Ampat” means “Four Kings” and comes from a local legend. The legend tells of 6 eggs that were found and from which 4 kings, a woman and a ghost hatched. In marine biology circles, the area is known as the global centre of marine biodiversity. It lies in the very centre of the Coral Triangle and is home to nearly 600 coral species and 1600 fish species. For comparison, the entire Caribbean has less than 70 species of coral.


Raja Ampat: Painemu Lagoon


Unknown to most people, the Birds of paradise found here and in the Halmahera region further west also played an important role in publishing the theory of evolution. Between 1854 and 1862 Alfred Russel Wallace traveled and conducted research in Borneo, Sulawesi, Halmahera. He was collecting specimens of all kinds of animals, amongst others the birds of paradise found in the region. His observations of these birds helped him develop his own theory of evolution, parallel to Darwin. Darwin had been working on his manuscript for many years, but was hesitant to publish any of it. A letter from Wallace to Darwin, in which Wallace explained his ideas, sparked Darwin to finally publish his magnum opus. Darwin presented the article “On the Tendency of Species to Form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection” in 1858 at the Linnean Society as a joint work from himself and Wallace. Once Darwin’s “On the Origin of Species” was published, Darwin ended up getting all the credit for the theory, but if not for Wallace and his birds of paradise, things could have turned out very different indeed.

While the birds of paradise are pretty amazing (we did go on land for a few hours to try and spot a few), the reason for this trip was to observe the diversity under water. This was the second time I dived Raja Ampat, and I can tell you it is fantastic. I’ve never dived anywhere else where the colours are so…everywhere, just everywhere. The quantity of soft coral, gorgonian seafans, corals, sponges, ascidians, etc is just staggering. You’ll find shades of every colour everywhere, some sites are so overwhelming that you’d almost forget to look for small critters and instead just float around to try and take it all in. Especially when there is a lot of sunlight and strong currents ensure all soft corals look like pink, orange, yellow, purple or white balls of fluff spread out over the reef. One such dive prompted the comment “This must be the campest divesite ever!”, and I couldn’t agree more. Many of the divesites around Raja Ampat look like the marine equivalent of letting a 6 year old kid decorate the Christmas tree…

soft coral

Explosions of colour (source)

Of course the diversity extends beyond corals, the fish life is just as great. It might be harder to find critters than Komdo or Lembeh, but there is a lot to make up for that. One of my favourites are the wobbegongs you find everywhere, especially at the northern divesites. But it’s also great to see all the schooling fish, and a very healthy amount of predators. We’ve seen a fair few sharks, tunas, Spanish mackerels, and other pelagic predators you don’t see very often in Indonesia. It’s also great to see lots of large groupers, since they are a very popular food-species, having a lot around means that protection is working and fishing pressure is not too high.

Fish soup

Fish soup in Pulau Daram

This protection can be credited to the efforts of many local and international NGOs working in the region. Their work helped motivate local and national governments to establish Indonesia’s first MPA (Marine Protected Area) network. Raja’s 15 MPAs protect nearly 6 million hectares of marine habitats. The area is also a shark sanctuary where capture and killing of sharks, rays, dugongs and turtles is prohibited. To me, knowing that this beautiful area is being protected in the best possible way makes diving it an even more rewarding experience.