Tawny Bumblebat

In the early morning, the stiff and fetid air of the Holmgamock forest hangs low. Beyond the ringing of cicadas and the chirruping of songbirds, a buzzing sound  occasionally flitters through the dense canopy. This peculiar droning doesn't originate from the usual suspects such as bees nor wasps, in fact, the buzzing seems to emit from a rotten log.

A closer look into this decaying log, reveals a surprising find. A group of 8 small bats, huddled around a significantly larger one in the middle. We've stumbled upon an increasingly rare find, a tawny bumblebat colony.

[Excerpt from Mossfells- Gardens of Life, Episode 4: The Coastal Forests]

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Status: Critically Endangered

The tawny bumblebat (Vomvos habitor - Buzzing dweller), is the only remaining member of the subfamily of pseudo-eusocial bats. Most members of the species are anatomically similar to microbat members of the family Vespertilionidae save for a few very distinct exceptions.

Tawny bumblebats live in colonies consisting of 4 to 50 members. Most of these members are rather diminutive, weighing at most 8 grams. However these are merely the workers for the colony. At the center of a bumblebat nest, a single queen bumblebat resides, weighing up to 1 kilogram.

Tawny bumblebats are a unique example of a mammal developing eusocial characteristics. The bumblebat "hive" works to provide food for their queen, their young, and each other. Unlike eusocial insects, both males and females are present in roughly equal ratios, and work in unison to sustain their colony. Bumblebats primarily are frugivorous and are well suited to consuming large amounts of fruit in the coastal rainforests of the archipelago. In order to feed their queen, workers store most of their ingested fruit in a special crop-like sac  which they then regurgitate. Tawny bumblebats also communicate with each other using a unique system of buzzing which they produce by rapidly vibrating their wing together. They are capable of using buzzing to signal when predators are around, changes in air pressure, and the presence of fruit nearby. 

Tawny bumblebats are of particular interest to scientists because they represent a species which isn't fully but is on the its way to becoming eusocial. In the absence of a queen, the smaller worker morphs are able to reproduce amongst themselves and do not exhibit as many eusocial behaviors such as food sharing. Tawny bumblebat colonies can survive in this state for years. However, certain females possess the ability to over produce pheromones which are normally used by infant bumblebats to signal hunger. The intensity of these pheromones causes other bumblebats to overfeed this female, eventually causing her to develop into a queen morph. The queen morph then produces a second set of pheromones which regulates the ovulation of her female peers, while increasing the virility of her male peers. 

Queen morphs can live up to 30 years while workers will live anywhere from 2 to 5 years. In the span of a month, a queen morph can have up to 10 offspring. The young will take only 4 months to grow to adulthood. Queen morphs retain the ability to fly, and can migrate with the colony to new locations, but generally prefer to stay in their original location. If the colony grows too large, a multiple queen morphs may arise and the colony will fracture, with each pregnant queen searching for a new location to establish themselves and ready to start their own colony.

Bumblebats prefer to nest in wooden enclosed spaces such as tree hollows, rotten logs, or old houses. Workers can artificially create walls and boundaries to nests with sticks and regurgitated soil, but most colonies will prefer not to adjust their surroundings. If attacked by predators, bumblebats will attempt to plug nest entrances with their bodies to shield their queen. 

In the modern day, bumblebats are an increasingly rare sight on the archipelago. Historically, they were present in many of the now urban areas of the Bountiful Isles and Neffannafjall until development pushed eliminated much of their original habitat. Their numbers have only recently and precariously plummeted due to several severe outbreaks of white-nose syndrome in 2010, 2017, 2018, and 2020. As of today, the tawny bumblebat population is estimated at only 200 remaining individuals mainly located on the island of Fernbank. Several initiatives have been promoted by NGOs to capture the last remaining colonies and begin captive breeding programs before this unique mammal in transition to eusociality is lost forever.