Panthera, a fabulous group that works for the conservation of big cats, puts up fascinating posts on their website. This one first appeared in mid-September 2018.
September 4, 2018
Mature male leopards are at least 60% larger than females, and broader, with larger chest girths and longer, bulkier heads. But there’s something else you may notice that sets males apart: Their thick necks can be adorned with a loose flap of skin hanging underneath. These skin folds are called dewlaps.
Dewlaps are observed in a variety of species throughout the animal kingdom, most notably in certain birds, lizards, and hoofed mammals. In mature male leopards, a well-developed dewlap is prominent and one of the best ways to determine age.
However, the function of leopard dewlaps remains unknown and largely unexplored. Since they are a sexually-dimorphic feature—meaning only one sex exhibits the trait—scientists speculate that this enigmatic ornament is linked to sexual selection or male fitness.
Of another conspicuous, sexually-dimorphic feature among cats—the mane of a male lion—Charles Darwin postulated: “[It] forms a good defense against the one danger to which he is liable, namely the attacks of rival lions.”
The idea behind this hypothesis is that adaptations such as body armor or weaponry, like antlers on male deer, increase the ability of males competing against other males. Most often the winner is the lucky male who gets to mate with the female and pass on his genetics.
On the other hand, results of more contemporary research indicate that injuries sustained during fights between lions don’t appear to differ between maned and non-maned sub-adult males or even females. This outcome suggests that the mane/neck area is not a high-target region during fights. Instead, observations find that the back and hindquarters seem to be the targeted areas during confrontations.
Many biologists believe that a male lion’s mane serves as an indicator of sexual fitness. Studies using life-sized toy lions sporting contrasting mane colors and lengths found that male lions were more likely to approach the imposters with lighter, shorter manes, while female lions were drawn more to models with darker manes. These results suggest that males with shorter, blonder manes are less intimidating to rival males, and thus perceived to have lower overall fitness.
We can apply this theory to hypothesize about the functions of a dewlap on a male leopard. However, fights between elusive male leopards are rarely observed and documented by scientists. This makes it difficult to confirm if the leopard’s dewlap has any defensive functions. Likewise, it’s hard to determine if it serves a similar purpose to that of a large, dark mane in sexual selection, as an indicator of fitness and longevity.
Another speculation about the dewlap is that it simply makes mature leopard males appear larger and more intimidating to rivals. Typically, as a male leopard ages, his dewlap enlarges. Mature males hold wider territories and have more opportunity to mate with females.
This also means that there are more opportunities to come into conflict with other males seeking the same territory and females. It would be ideal to avoid physical confrontation, and potential injury, by being able to display fighting capability and fitness, thus deterring potential rivals without physically engaging them. Fighting with other males has potential to lead to injury or death. Even the smallest injuries can fester and inhibit hunting abilities, leading to a decline in body condition that could result in death.
Younger and smaller males may be dissuaded from engaging in a fight with a larger male sporting a more pronounced dewlap. Alternatively, estrous females may select a male with a larger dewlap, perceiving him to have greater fitness than his peers. As of yet, no studies have been conducted to determine if dewlap size correlates with testosterone levels or is linked to reproductive success as an indicator of longevity.
