African straw-colored fruit bat
The straw-coloured fruit bat (Eidolon helvum ) is a large fruit bat that is the most widely distributed of all the African megabats. It is quite common throughout its area ranging from the southwestern Arabian Peninsula, across forest and savanna zones of sub-Saharan Africa. It is listed as Near Threatened on the IUCN Red List due to a decreasing population trend. Straw-coloured fruit bats travel in massive colonies of at least 100,000 bats and sometimes massing up to 1 million. From October to end of December every year, in the largest migration of mammals on the planet, up to 10 million straw-coloured fruit bats congregate in Kasanka National Park, Zambia, roosting in a 2 hectare area of Mushitu forest each day. This migration was only discovered in 1980. Their necks and backs are a yellowish-brown colour, while their undersides are tawny olive or brownish.
Straw-colored fruit bats are native African animals, called so due to the bright orange, yellow or brownish fur, surrounding their throat, stretching onto the back of the neck, and covering the special glands, which produce a specific musky-smelling fluid. This substance is usually brighter in color and more noticeable in males. Additionally, male individuals are bigger and exhibit darker overall coloration. Young individuals, on the other hand, are distinguished by the absence of a collar around their neck as well as darker coat, compared to mature bats. The straw-colored fruit bat is the second largest bat species, found in Africa.
Straw-colored fruit bats are native to Africa, occurring in equatorial and sub-Saharan regions of the continent. The natural range of this species stretches from the southern tip of the Arabian Peninsula to offshore islands such as Zanzibar and Pemba. In addition, they are known to migrate to southern Africa, reaching Zambia, Malawi, and Mozambique. These bats are highly adaptable creatures, capable of living in different types of habitat, from moist and dry savanna to urban areas. Overall, straw-colored fruit bats generally inhabit moist and dry tropical rainforests such as riverine and coastal forests and mangroves.
Straw-colored fruit bats are a highly social species, forming extremely large groups known as colonies. A single colony of these bats may contain from thousands to as many as millions of individuals. Meanwhile, each such colony consists of small units (clusters) of up to 100 bats. Although they are nocturnal feeders, most activity occurs during the daylight hours. Most of their active hours are spent resting and moving around their roosting site. During the night, the colony splits into smaller groups, which leave to forage in nearby forests and plantations. These animals maintain the same diet throughout the year. However, they may occasionally migrate, when the usual types of food are not available or scarce. During these periods, they remain in these large colonies rather than splitting into smaller groups. The communication patterns of this species are unknown, but they evidently make a loud noise in their large colonies. Additionally, these animals are likely to vocalize when eating and roosting.
As the common name suggests, the Straw-colored fruit bats maintain a herbivorous (frugivorous) diet, particularly favoring dates, baobab flowers, mangoes, papaws, avocado pears, figs, passion fruit, custard apples, loquats, bark, and nectar. They may also consume other types of food such as flowers, buds, and young leaves.
The reproductive system of this species is currently unknown. However, as mating occurs in colonies, it may mean that they exhibit a polygynous mating system. Breeding occurs during late spring, from April to June. Although implantation is sometimes delayed, it generally takes place during October. In December-January, females yield a single, altricial baby in so-called ‘maternity colonies’, formed by clusters of females. In populations, where young are born undeveloped, the gestation period lasts for 9 months, after which the babies continue to grow for additional 4 months. Meanwhile, populations without delayed implantation exhibit shorter gestation of only 4 months. The newborn bat cannot fly and totally depends on its mother. The nursing period lasts for around 4 months, after which the young bat has learned to forage independently. The baby is weaned during the period of abundant food, which coincides with the peak of the wet season. The age of reproductive maturity is 2 years old.
Although Straw-colored fruit bats are abundant and commonly found throughout their range, populations in some areas are affected by adverse factors. Thus, Straw-colored fruit bats in West and Central Africa face large-scale hunting for food. In other areas, these animals are hunted for medical use. Localized threats also include persecution and hunting as pests.
The IUCN Red List and other sources don’t provide the number of the Straw-colored fruit bats’ total population. As reported on the IUCN Red List, these bats are quite common across their range, found in very large colonies, varying from thousands to millions of individuals. Nevertheless, a colony in Kampala (Uganda) has undergone a sharp population decline, decreasing from 250,000 to 40,000 bats during the last 40 years. Overall, this species’ numbers are decreasing today, and the animal is currently classified as Near Threatened (NT) on the IUCN Red List.
Straw-colored fruit bats are vital pollinators of certain flowers throughout their range. Due to their diet, these bats also act as seed dispersers, which they do through their feces. Overall, these animals are irreplaceable in sustaining their rainforest habitat, which would simply disappear without these bats.
