Will seahorses change mates?

Dear Carrie:

Kris is correct. In captive conditions, when seahorses are maintained in groups and provided with a choice of partner, promiscuity is fairly commonplace. The most recent studies done on the subject suggests that the stallions are more likely to remain faithful to their mate, whereas the fickle females are more likely to stray when the opportunity presents itself (see the study synopsis at the end of this message). Of course, Mustangs and Sunburst will interbreed freely, so there’s no saying for sure which of the prospective partners may eventually select Zack as her mate.

In the aquarium, it’s pretty common to see trios or small groups of seahorses engaged in courtship together, but when the big moment comes the female will pick one of her suitors to mate with and deposit all of her eggs in one basket, so to speak. As a rule, the female deposits all of her eggs in a long, continuous sticky string during one brief belly-two-belly bumping during a successful copulatory rise, which only takes a matter of seconds (over 1600 eggs can be transferred to the male 5-10 seconds). Eggs may be spilled and dropped on the bottom if the connection is not perfect, but ordinarily all of the mature ova are hydrated and extruded at once. In most species, the female cannot divide up her clutch of eggs among different receptive males.

However, it is not at all uncommon for the female to choose a new partner and mate with another one of her suitors during her next reproductive cycle, depositing all of her ova with this new male during a single copulatory rise. I find that seahorses are often not at all monogamous in captivity when they are kept in groups and have a choice of partners.

Captive-bred seahorses are far-different animals than their wild conspecifics in that respect when it comes to their breeding habits. They are raised at far greater population densities than wild seahorses ever experience, and are accustomed to living in close proximity to others of their kind and to having a selection of possible partners to chose from when mating. As a result, farm-raised seahorses are highly social animals and appear to be far more gregarious and more promiscuous than their wild counterparts.

Captive-bred seahorses do indeed pair bond, but the attachments they form are by no means permanent. A couple may stay together for a single mating or for several breeding cycles (Cozzi-Schmarr, May 2002). When provided with a choice of mates, however, they are apt to swap partners for no apparent reason after any given mating, and generally seem to enjoy exploring different pairings (Cozzi-Schmarr, May 2002). One sees this all the time when adding new specimens to an established tank. The introduction of the new arrivals triggers a renewed flurry of greetings and other interactions and kicks the general activity level up a notch as all the seahorses reassess the shifting social dynamics of the herd and check out prospective new mates. Chances are great the next breeding cycle will see some new pairings.

It has certainly been my experience that when seahorses are provided with a group of potential mates to choose from, they will take advantage of that situation to try different pairings. It is very possible that this polygamous behavior may simply be an artifact of captivity, the inevitable result of keeping seahorses in small closed-system aquaria where they cannot maintain anything approaching the large territories they are said to enjoy in the wild. But it is a fact that polygamy is the norm for seahorses in the captive environment when they are maintained in groups, and that monogamy tends to break down in such situations.

Interestingly, it is fairly easy to predict which couples are likely to remain together and which pairs are apt to wind up with new partners next time around. Pairs that continue to conduct daily greetings in the aquarium are very probably going to re-mate when the male delivers his next brood. But all bets are off when a fickle filly proceeds to flirt with males other than her mate while he is carrying young. She is liable to bestow her eggs with one of the other available males when the next breeding cycle begins. It is the female who initiates daily greetings, and if she chooses not to renew her bonds with her current mate each morning, it’s a very good sign that this mare is moving on to greener pastures.

Eventually, these brazen broodmares are apt to give all the studs in the stable a roll in the hay. Presented with the option, it is sound genetic policy to diversify and try different combinations of genes. I suspect the only reason this doesn’t occur more often in the wild is a lack of opportunity.

Here is a brief summary regarding the recent study on the mating habits of seahorses I mentioned earlier:

BBC News/UK/England/Norfolk
Last Updated: Tuesday, 29 August 2006, 07:23 GMT 08:23 UK

Study shows seahorse promiscuity

The sex life of the female seahorse is being investigated in a research project under way at a sea life centre.

The spotlight is on tropical seahorses at Great Yarmouth Sea-Life Centre as scientists examine whether females are more promiscuous than males.

The seahorses have been fitted with tiny coloured necklaces so researchers can see who is pairing up.

It had been thought seahorses mated for life but early results show the females being more promiscuous.

Seahorses at the centre mate frequently and researchers have enlisted the help of visitors to tell them which coloured tags are pairing up, giving a date and time.

The survey will then be added to eight others taking place across Europe.

Terri Harris, one of the researchers, said: "Early results are showing us that the males stay faithful to one female.

"However the females may have more than one male partner so they are the ones who are more likely to stray."

Click here: BBC NEWS | UK | England | Norfolk | Study shows seahorse promiscuity
http://news.bbc.co.uk/2/hi/uk_news/england/norfolk/5294326.stm

Best of luck with your captive bred Casanovas, Carrie! It could certainly be that they are trying to switch partners, which will ultimately be determined by the females. One way or another, here’s hoping they pair up and produce many broods of healthy young for you in the weeks and months ahead.

Happy Trails!
Pete Giwojna