You might think from the scientific name that this is a close relative of the vampire bat but, while it does belong in the same family, vampire bats are a side-branch of that family thought to have diverged from the main branch around 50 million years ago. Its closest relative may be the far less fearsomely named "big-eared woolly bat" (Chrotopterus auritus), with which it shares some of its unusual feeding habits.
In fact, the spectral bat (or "ghostly bat" in the original Latin) is one of the species listed in the first recognised catalogue of scientific names, published in 1758. The vampire bat was not scientifically described until 1810, over half a century later. Neither species was originally given the generic name they have now, but, under the mistaken impression that they drink blood, French naturalist Constantine Rafinesque nabbed the name Vampyrum for the spectral bat before anyone had given one to the vampire bat.
The spectral bat is the largest bat living anywhere in the Americas. Adults weigh an average of 180 grams (6½ oz.), which may not sound very much, but it's important to remember that bats have hollow bones and a light frame to keep them airborne. For example, the big brown bat, a very common species in the US, and not exactly small itself, weighs only around 20 g (0.7 oz.). So a better illustration of just how big this bat is is to look at the wingspan, which can easily reach 90 cm (3 feet).
Moreover, the spectral bat is carnivorous. Not just in the ecological sense of eating animal matter such as insects, but properly predatory. I discussed this three years ago, when I mentioned that this species is both the largest predatory bat, and the most purely carnivorous, with around 90% of its diet consisting of birds and small mammals - including other bats. They live north and west of the Amazon, from Guatemala and Belize in the north down to Bolivia and neighbouring parts of Brazil in the south, reaching as far east as French Guiana to the north of the jungles.
Other than tropical rainforest, they seem happy in almost any type of tropical woodland, although they prefer lowland evergreens. Despite their wide range, they are relatively rare, with individual groups being small and widely spaced, so that, combined with local forest loss, they are considered endangered in some countries they inhabit, if not as a whole.
Like many bat species, however, we know relatively little about its habits and behaviour, beyond the fact that they are monogamous, with a mated pair staying together to raise their children in relative isolation, rather than as part of some large colony as cave-living bats tend to. Based on that, we might suppose that they are fairly antisocial animals, lacking the complex communication and cooperation seen in some colonial species. But is that really true?
In November 2023, researchers placed a video camera inside the roost of a family of spectral bats living in a tree hollow in Costa Rica. Triggered by activity within the roost, the camera recorded the behaviour of the bats over the following three months, and the results of the analysis have recently been published.
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The family consisted of four bats, two parents and a pair of their young. The researchers note that, after the study period had concluded, the larger of the two young bats left the roost for good, and the adult female gave birth to a new pup shortly after. So, at least for this roost, four was the maximum they were prepared to put up with.
The bats, especially the larger adults, frequently brought food home to their roost, in the form of dead rats, mice, and birds. While we obviously can't know how many other prey items they had simply eaten on the spot, carrying food to a secure place to eat it is hardly unusual. What we'd perhaps expect, though, especially for a relatively antisocial species, is that the successful hunter would then eat whatever they had caught themselves.
That certainly did happen, but only around a third of the time. More commonly, however, another bat would approach the one with the food, calling out as it did so, and take a nip at the food item. At which point, the hunter would normally hand over the food, and they would both head up to the main roosting location, and the one who now had the item would eat it while the original hunter, and the other two bats, calmly waited for it to finish.
In other words, what we have here is clear cooperation: one bat brings home food for another, and everyone seems to respect that that's what's going on. On one occasion, there appeared to be a misunderstanding, with the two bats engaging in a tug-of-war over the food, but mostly it works peacefully. This is unusual for bats, although there are some instances of mothers feeding their young with pre-chewed food just prior to weaning, or nectar-feeding bat mothers regurgitating food for their pups. Here, however, it's happening between adults in a mated pair, or at least between adults and their weaned subadult children.
In this respect, it may be relevant that two children were living with their parents and that, since bats don't generally give birth to twins, we can assume they were different ages. This implies that the older one had stayed with its parents for a long time (since they would have to be at least 2½ years old), and that these particular bats may have an extended period of parental care. Part of that may involve adults provisioning their young with food - and the fact that the male is sometimes the one doing it is unusual since (unlike birds) male mammals rarely do this sort of thing. The adult male bringing home food for his mate may also allow her to remain in the roost and care for her young when they are still vulnerable and relying on her for milk, since they aren't weaned for about two months.
There are other indications that the bats are not as antisocial as we had previously thought. It had always been believed, for example, that spectral bats hunt alone. That's generally true, but in several of the videos a pair of bats left and then returned to the roost together, suggesting they may have foraged as a pair. This was often a parent and one of the subadults, perhaps indicating that the younger bat was being taught how to hunt.
When they weren't eating or out hunting, the bats spent a lot of time huddling up together. They would press together in a ball of two or more individuals, with at least one of them hugging the others by wrapping its wings around them, gently grooming their fur and making friendly noises. The huddling part is common for bats, but while all species groom themselves to clear out parasites and the like, only a few are known to groom each other. This, of course, is something that most primate species do all the time, and it has an obvious role in social bonding, both between parents and children and between the members of a mated pair. So, again, unless we're missing behavioural data on other bat species (which is certainly possible), spectral bats are unusually sociable.
The two subadults also played with one another, either engaging in a little play-fighting, as siblings are wont to, or chasing cockroaches that had got into the roost, perhaps as practice for hunting. On some occasions, they played with the camera, which was positioned well above their usual resting place. This is most common in species with extended parental care, supporting the data from the presumed age of the older subadult in this particular roost.
They may be ruthless predators with a spooky name, but spectral bats turn out to be surprisingly friendly and convivial, if only with each other.
[Photo by Matt Muir, from Wikimedia Commons, picture by Eduard Schmidt, in the public domain.]
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