Jul 28

Devious Dung Beetles, Cunning Cuttlefish and Lady-boy Lizards; How Nature’s Geeks get the Girls

lizard

In a Simpsons episode, Homer declares to Marge “there are two kinds of people, jocks and nerds”; and remember the captain of the football team, the big buff guy most of the girls seemed to fancy. Then there’s the gym junkies who hit the town in tight shirts to show off their muscles in an attempt to attract the ladies. For the rest of us meagre males we have to employ less direct approaches to attract a mate, whether it be by being smart, funny or (to the disdain of most females), sleazy. This idea is personified in the 80’s Molly Ringwald classic “Pretty in Pink” as the female lead chases the good-looking, popular kid, while friend-zoning her geeky pal who is obviously in love with her.
Well it seems that almost every animal group has its very own version of jocks vs nerds. In the world of biologists, the nerds are known as “sneaker” males and these guys can be quite successful with the females. Sneaker males employ a variety of methods, taking the ongoing struggle between brains and brawn beyond the silver screen.

Large male dung beetles construct tunnels within which they keep harems of females that they will vigorously protect, guarding the entrance to the tunnel from other males. The smaller sneaker dung beetles are no match in a physical contest with the big bruisers, so they will move out of site of the larger individuals before beginning construction on their own tunnel. Once beneath the surface, they make a bee-line towards the defended females where they will procreate undetected before slipping out the proverbial “back door”.

This variation in body types between males within a population is known as “polymorphism” and perhaps the best known example is in the Side-Blotched Lizard, Uta stansburiana. In this species there are three types of males identified; they are the orange-, blue- and yellow-throated. The orange-throated males are big, aggressive and control large territories often containing several females. The blue-throated males are slightly smaller, and work together to maintain small territories which contain only one female. The yellow-throated males are the smallest, control no territory and their markings make them look more like females. The yellow-throated males are able to sneak into the orange-throated territories and while his larger compatriot is on the lookout for the blue-throats and other orange-throated potential threats, he mates with all the ladies before sneaking back out. Because the blue-throats usually have only one female in their territories, they easy recognise the sneaky yellow-throats and chase them away. This produces what some scientists have likened to a scissors-paper-rock relationship in the male population of side-blotched lizards with no one body type able to dominate and out-breed the other two.

Perhaps my favourite example of sneaker males exists in the Giant Australian Cuttlefish, Sepia apama. During the breeding season, males can become very competitive and aggressive towards one another with on average four, but up to 11 males competing for a single female. It stands to reason that in this environment, the biggest and strongest cuttlefish will get the most girls, sometimes even maintaining harems to ensure they have access to a number of females at any one time. Sneaker males in this species employ a range of strategies to avoid conflict with the more macho individuals. Sometimes they will change the appearance of their skin and hide some of their tentacles, making them look like a female before being let into the harem and then sowing their seeds. At other times, they will stay hidden and wait till another male challenges the current “champion” and while they fight, slips in and slips out again; both figuratively and literally (although not really as cuttlefish are external fertilisers). DNA analysis shows that the success of these strategies is close to that of the “traditional” cuttlefish approach to reproduction.

However, let’s not forget that the girls in most species really have the final say in who they breed with and what traits they would like their offspring to possess. Breeding with big aggressive males has its downfall as conflicts can lead to collateral damage for the girls. Sometimes a sneaker male is chosen as a superior mate because to be sneaky can be more difficult than being strong, hence showing a greater potential “fitness” and increasing the chances of survival for the next generation.

So for you single scrawny guys, remember there is more ways to attract a girl than flexing your biceps and for the single ladies, don’t dismiss the geeks because they probably went to a lot of effort to get to you in the first place.

Byrne.