When it comes to mating rituals, reptiles probably aren’t the first group that comes to mind. After all, the spectacular songs and bright plumage of many kinds of birds do take a lot of beating – while courtship calls and displays can even be found amongst some of the frogs and newts.
It seems an odd state of affairs, particularly when you consider the reptiles’ evolutionary position – neatly sandwiched between their bird descendants and their amphibian ancestors – but reptiles haven’t entirely missed out on advertising for love. Some of their mating rituals are fairly straightforward, but others are more than a little unusual – and one or two are just downright strange.
Signalling With Sound
Although reptiles aren’t normally the most vocal of animals, sound does plays a part in their breeding rituals, and most particularly amongst the crocodilians. Male Nile crocodiles ( Crocodylus niloticus) for instance, make an awful lot of noise when they want to attract females, slapping their great flat heads onto the surface of the water, bellowing loudly and squirting mini-fountains out of their nostrils. It’s a competitive display, with males trying to out-do each other in their desire to get the best chance in the mating stakes, and there have even been cases of over-eager males getting hold of entirely the wrong idea and responding to a perceived ‘display’ coming from an entirely non-crocodile rival. One of the most bizarre examples of this was reported at the end of 2010, when crocs at the Hamat Gader park in Israel began replying to the sonic booms generated by Israeli war-planes flying overhead – two months ahead of the real breeding season.
The Nile Crocodile isn’t alone in using sound to attract a mate. The distinctive swelling on the nose of male Gharials (Gavialis gangeticus) helps provide a resonance chamber for its particular mating hum, while the American Alligator (Alligator mississippiensis) uses very low frequency infrasound to make the water dance and shimmer along his back.
With many reptiles having well developed colour vision, visual displays also feature at breeding time. Lizards in particular use this approach – ranging from adopting a characteristic breeding colouration, to the more familiar territorial-type displays of head nodding and bobbing, or, in suitably-equipped species, dewlap flashing. Britain’s own rare Sand Lizard (Lacerta agilis) is a good example, the males discarding their normal, year-round and fairly anonymous brown colour scheme, in favour of turning partly, or entirely green, at breeding time.
For some kinds of lizards, making the most of your ritual display needs a few nifty dance moves too. In the case of the Eastern Fence Lizard( Sceloporus undulates), for instance, the males have bright blue throats and similar coloured patches on their belly, twisting their bodies to show them off to potential mates during courtship. Any female that isn’t ready to mate, or simply isn’t impressed by the display of her erstwhile suitor, will arch her back upwards and jump off to one side – a clear indication of “thanks, but no thanks!”
Scent and Deception
Smell has a role in mating rituals amongst a number of reptile species, with Garter Snakes (Thamnophis sirtalis) and their close relatives probably providing one of the best examples. After a period of around two weeks of brumation – a state of hibernation-like dormancy, where the animals eat nothing – female garter snakes emerge and release a distinctively smelling sex pheromone to signal their readiness to breed. Hordes of hopeful males then descend upon the female and compete furiously with one another in an attempt to mate with her – sometimes resulting in a tangled ball of twenty or more of the smaller males per female.
Apart from sounding a bit like some kind of nightmare version of a TV perfume advert, it all seems quite straightforward, but in amongst all of this is one of those times when reptile ritual goes a bit strange. Some of the males, it seems, release ‘female’ pheromones alongside their male scent – leading to obvious confusion amid the rest of the males, which can result to them attempting to mate with the she-male they’re following.
Quite why this happens is not entirely understood, but one thought is that the ‘fake’ female gains warmth and protection from the close company of the other males, while other researchers have suggested that it may be a ‘selfish gene’ ruse to improve the chances of males related to these ‘she-males’ actually breeding with a real female, by diverting the competition. Either way, it’s an odd carry on!
A Strange Case
Even odder, however, is the case of the Desert Grassland Whiptail (Aspidoscelis uniparens). The clue to the fact that this little lizard from Texas, Arizona and northern Mexico has an odd method of reproduction lies in the scientific name “uniparens” – it’s an all-female species and the young are born by a process known as parthenogenesis, commonly described as ‘virgin-birth.’
There’s nothing new about parthenogenesis in the world of biology; many animals use it, including surprisingly common-place ones such as aphids. What makes this particular instance a little different is that for this lizard, there’s a need for female/female courtship, followed by a mating – technically called a “pseudo-copulation” – before either partner can actually produce eggs.
Reptiles may not be the first type of animal that springs to mind in a discussion of mating rituals – but there’s no denying that they do have their own way of doing things!