Most of us spiff ourselves up when we're looking for love.
But some males in the animal kingdom go a lot farther than a bit of extra grooming, drastically changing their physical appearance to catch the attention of females. Male hormones, such as testosterone, usually trigger these seasonal embellishments.
Massive antlers on moose and other deer are the most obvious and startling, but we wondered, how much of a makeover do more unsung males go through to snag a mate? (Related: Why Do Moose Shed Their Antlers?)
Frogs and Toads
Males of many toad and frog species, like the European common frog, develop muscular "Popeye arms" and nuptial pads during mating season, says Greg Pauly, curator of herpetology at the Natural History Museum of Los Angeles. (Read about a newly discovered frog mating position.)
Nuptial pads are raised, keratinized areas—like a sandpaper patch—on the male's hands that allow him to hold onto the female's slippery skin during mating.
Increased muscle mass in the arms make it easier to hold onto females should another male try to break up the copulating couple—or if the female tries to "dislodge an unwanted suitor by passing beneath a low branch or exposed root," Pauly says.
The nuptial pads develop with sexual maturity and if the species has them they stay for life, becoming more pronounced during breeding season.
The great crested newt will see your arms and pads raise you a full-body mohawk.
These members of the salamander family, native to Europe and Western Asia, are "one of the most dramatic 'changers' of all," Pauly says.
Like many newt species, they start out as aquatic larvae, then move onto land as juveniles. As adults they return to the water to breed. (Also see "New Frog Mates Doing Handstands, Does 'Pottery.'")
Each breeding season, mature males develop muscular arms and nuptial pads as well as tail and body dorsal fins, which make them look bigger and more impressive to females and each other. and each other. These newts have a lek mating system, meaning males congregate in one part of the pond and females come and choose among them, and part of that display is letting other males know not to mess with their spot in the lek. Males also lash and fan their tails during courtship displays, both showing off and sending pheromone scent cues her way.
Some salmon species undergo "a major remodeling of the lower jaw for breeding purposes," Scott Heppell, associate professor of fisheries at Oregon State University, says via email.
The males' lower jaws develop a hook, called a kype, which they use to fight other males.
Sockeye salmon in particular undergo a major change to their skull structure during spawning, he says.
But unlike amphibians, sockeye males don't go back to their less impressive physiques after mating—the fish begin to degrade and die after their final act.
Drumfish, toadfish, and midshipmen are related species that have some less obvious but no less impressive transformations.
When it's time to breed, their sex hormones bulk up muscles along their swim bladders, enabling the fish to vibrate the organ and create loud sounds (listen) that act as a siren song for females, Hepell says.
The hum is so loud that in Sausilito, California, in the 1980s, houseboat owners complained of a noise disrupting their peace and quiet that turned out to be a midshipman serenade.
These marine mollusk males grow gonads up to half as much as their body weight during mating season. The beefier gonads allow for more sperm production, all the better for spreading their genes.
But that's not the only trick they have up their shells.
Slipper limpets live and mate in stacks (see video) with a female on the bottom and smaller males on top.
These males try to mate by extending their lengthy penises—which are sometimes as long as their whole body—under her shell where she sheds her eggs. (Read about how barnacle penises can be eight times the length of their bodies.)
Males that don't attach to an existing stack can attach to a surface on their own instead, in which case they can become female.
That’s incredible, Mr. Limpet!