While most of us are used to imagining butterflies eating only nectar for nourishment or occasionally pollen, the truth is that their diets are a whole lot more diverse.
These diets include all sorts of disgusting things, from mud to rotting plants, animal sweat and excrement, and finally to the decaying flesh of dead animals.
If you’re wondering exactly why butterflies eat dead things, there is a good reason, and it’s not to do with hunger.
The practice, known as “mud-puddling” due to being for the same reason that butterflies land in mud to drink from it, is often done by the male butterflies to collect nutrients to improve their own reproductive capabilities and even to offer as nuptial gifts to the females.
The rest of the article will help us understand the importance of mud-puddling to butterflies and hopefully be able to look at it from a new and more appreciative perspective. It will also enable us to learn to recognize where and when it happens.
Do Butterflies Eat Dead Things?
Although it may seem strange, it is perfectly normal for butterflies to eat dead things. It’s less common for female butterflies to do so, but not unheard of.
Different species of butterflies eat carrion at different rates and at different stages in its decomposition, with most true butterflies preferring it in the stage of advanced decay while the closely related moths will favor dry carcasses.
Butterflies don’t have the kinds of mouths we’re used to thinking of, and instead each have a proboscis, a long, tube-like organ used for sucking in whatever food or matter the butterfly wants to consume.
It is precise because they have this proboscis rather than teeth that they can only eat large animals once they’re already dead, and even then, only after they’ve reached an advanced state of decay.
In this state of decay, the butterflies are able to suck up the liquefying nutrients in a way that they would simply not be able to if the animal was still alive.
The range of dead animals that butterflies eat is very broad. In common with most scavengers, butterflies will, if they need the nutrients, feed on most carrion, and known examples of butterfly bait include snakes, lizards, fish, shrimp, pigs, dogs, and even prawn paste.
Animal carcasses hanging from branches, whether following a natural death or placed there as bait, are a common way of attracting butterflies that typically stay in trees.
Why Do Butterflies Eat Dead Things?
Butterflies aren’t always able to satisfy all of their nutritional needs from nectar. Sodium deficiencies, for instance, will often lead a butterfly to land on people to suck up their sweat, or in a more disgusting variant, lead it to drinking from a puddle of urine.
Dead things are very good sources of all sorts of nutrients, including sodium, so they become natural targets for butterflies who need this boost.
The amino acids and salts that are often absorbed with the carrion fluids also provide the necessary nutrients for male butterflies to produce sufficient sperm as well as pheromones, which are a crucial part of their ability to attract a mate.
More than being an addition to their diet, it’s an essential part of their reproductive strategies.
The Biological Journal of the Linnean Society investigated in 2005 the extent to which male butterflies mud-puddling on various types of matter, including dead things, is a part of preparing and offering nuptial gifts to female butterflies.
Males of multiple species of butterfly have been observed collecting the nutrients from carrion and including it in the spermatophore, a mass consisting primarily of the sperm for fertilization, before transferring it to their female mates.
This not only provides valuable nutrients to the females in the moment, but also frees them from having to seek out these nutrients themselves, thus leaving them less vulnerable to predation.
What Butterflies Eat Corpses?
It is primarily the male butterflies that eat corpses, although female butterflies are known to practice mud-puddling as well when in need of nutrients.
With that said, when various species of butterflies were dissected to measure their sodium concentrations, the species with the highest levels of sodium in the spermatophores were those where mud-puddling was uncommon among the females, whereas in species where females ate decaying flesh regularly, the spermatophores that the males delivered to them had significantly less sodium.
Mud-puddling practices also vary between species and families.
The Journal of the Lepidopterists’ Society investigated these variations in 1969 and found interesting differences, including that most members of the lepidoptera order prefer carcasses in advanced decay while a minority prefer them only once they’re dry, and that skipper butterflies were uniquely attracted to carrion before it would reach the stage where it was liquid enough to be eaten by them.
Some species of butterfly have even evolved to specialize in the effective consumption of decaying flesh. Nymphalidae, the most common family of butterfly, also show the broadest range of strategies for gathering nutrients via mud-puddling, including from animal carcasses. It is believed that some species are even able to smell carrion from long distances, enabling them to have access to these essential nutrients as soon as possible after they require them.
We’ve learned in this article that the common belief that butterflies only eat nectar is a misconception, and a butterfly’s actual diet is a lot more varied due to the broad range of nutrients they require. We can identify mud-puddling as a wider practice, where it includes eating sweat, rotting fruit, and animal waste in the same way and for the same reason that butterflies eat decaying flesh. We know that nutrients from carrion are essential to many male butterflies’ reproductive capabilities, both in aiding sperm production and in offering nuptial gifts to the female. At the same time, we found that in some species of butterfly, the females are more than capable of doing their own mud-puddling, and the males compensate for this by depositing less nutrients in their spermatophores. So, do butterflies eat dead things? They do, but at differing levels depending on species, sex, and needs.