Just south of the Sahara Desert, a medium sized moth flits through the hot air, passing through moonbeams before landing on a branch. Sensing danger lurks nearby, it creeps into a deep shadow, hiding itself from the prying eyes of nighttime predators. Convinced it’s concealed and safe, it’s wings flutter. That’s all it takes, a single wingbeat, for a bright orange, Sundevall’s roundleaf bat (Hipposideros caffer) to pinpoint the moth’s exact location. Before the moth has a chance to complete a second wing beat, the bat alters it’s coarse and bears down on the unsuspecting moth, snatching it from its hiding place and quickly devouring it before hunting for yet another moth with which to feed its voracious appetite.
Other names frequently used in relation to this species include:
- Cape Leaf-nosed bat
- Common African Leaf-nosed Bat
- Lesser Leaf-nosed bat
- Sundevall’s Leafnosed Bat
Identifying Sundevall’s Roundleaf Bats
Size-wise, the Sundevall’s bat is right in the middle of the spectrum for microbats. It’s body measures between 3.1 to 3.5 in (8-9 cm) and its wingspan is 7.9 to 11.4 in (20-29 cm.) The average adult weighs between 0.28 to 3.5 oz. (8-10 g.) Juvenile Sundevall’s Roundleaf bats have a lovely soft gray fur that turns into a stunning orange as they reach adulthood while their wings remain a complimentary shade of brown. Like many bats, the fur on the bat’s belly is a shade or two lighter than their back fur.
When scientists catch a representative of the species in a mist net, they look closely at the animal’s ears and nose while confirming species. A Sundevall’s roundleaf bat has ears that are quite large in comparison to the size of its skull. The elegant ears are shaped live an oval leaf and feature an antitargus that’s attached to the earlobe.
Like all members of the Hipposideridae family, the Sundevall’s roundleaf bat has a nose-leaf in the shape of a horse shoe which helps them direct their echolocation calls. On each side of the U-shaped leaf is a small but very distinctive projection that is crucial for identification. Just behind the leaf is a ridge of rippled skin.
The Sundevall’s Roundleaf Bat’s Lifestyle
The Sundevall’s Roundleaf bat enjoys a large range that includes everywhere but the central forested regions of the portion of Africa that lies below the Sahara Desert and the southwestern Arabian Peninsula. Mist net captures have also taken place in portions of Zanzibar, Morocco, and Pemba. The species thrives in savannas where colonies of several thousand bats are found roosting in caves and hollow trees. Colonies have even occasionally been known to turn an old, abandoned building into a roost site.
Sundevall’s Roundleaf bats prefer dining on moths over all other available insects. Approximately 92% of their diet consists of moths, though they’re sometimes selective about the types of moths they’ll eat. They’re particularly adept at avoiding arctiid moths which have a foul taste. The bats are able to identify the arctiid moths by the distinctive ultrasonic clicks the moth emits. When unable to find any moths, members Sundevall’s Roundleaf bats will also eat soft bodied flies and even the occasional beetle.
While Sundevall’s Roundleaf bats have the remarkable ability to isolate a landed moth by the sound of its wing beats and scoop them up, they prefer catching moths that are in flight.
While the bat’s wings aren’t shaped for bursts of speed, the shape does allow the bat to enjoy a high degree of maneuverability and to even hover in mid-air when necessary.
While geographical location does have some influence over this species sound, as a rule of thumb, their echolocation call frequency is right around 140 kHz with a 6 ms constant frequency component and a brief frequency-modulated downward sweep
Bringing up Baby Sundevall’s Roundleaf Bats
The species mates during the winter and the females, using delayed implantation, will often wait up to seven months before allowing herself to become pregnant. She gives birth to a single pup (though twins might occasionally happen) after a three-month gestation period. While in utero, the pups develop deciduous teeth which aren’t present at the time of their birth.
At birth, Sundevall’s bat pups are hairless and completely helpless. They cling to their mother who not only feeds them and keeps them safe while in the roost, she also carries the pup with her when she goes out to hunt. This process goes on for a few weeks until the young pup is old enough to stay in the roost without his mother for a few hours.
Near the pup’s one-month birthday, it’s strong enough to start flying short distances and learning how to hunt for itself. The mother generally weans the pup when it’s about three months old.
In addition to large colonies, the species also forms smaller, harem style maternity roosts, something that researcher Gary P. Bell spent time observing during the 1980’s.
After exploring the area near Zimbabwe’s Sengwa Wildlife Research Center finding a hollowed out baobob tree that served as a roost for a maternity colony. He visited the tree on 12/27/82 and noted that in addition to one male, which he caught and marked with a colored ring, the colony consisted of 7 females and each had a nursing pup.
On 1/2/83, he noted that the colony still had an equal number of females and babies, and that the same male was also present. Using mist nets, he’d set up near the tree, he was able to catch and tag 24 different females and pups. While he was working, he observed that approximately 50 bats were flying near the tree.
The next time Bell made the trek out the tree, he found 15 bats in residence. The same male, 9 tagged females, and three tagged pups. The rest of the mother pup combinations weren’t tagged.
The next visit took place on 1/27, at which time the only bat Bell found at the tree was an unmarked, dead juvenile. This was Bell’s last visit until 3/7 at which time the pups should have been weaned. When he looked in the roost, he was greeted by two of the marked juveniles as well as 16 unmarked companions who looked approximately the same age. There were also three banded females in the roost
I’ve not found any information that explores how the males connect with a particular harem, or if the harem consists of mothers and daughters or other closely related female groups.
We do know that this isn’t the only species of neo-tropical bat that forms harem style maternity colonies. While it’s not entirely clear why the bats choose to do this, one theory is that it’s the male bats job to help ward off threats or distract predators, allowing the females to focus their energy on raising pups. Another possible explanation is that this setup leads to better utilization of resources. It’s also unclear if the females stay bunched up in the same harems when the join larger colonies, or if they simple mingle with the masses.
A Little Something Extra
One of the Sundevall’s roundleaf bats most interesting identifying features is a bonus pair of teats. They’re found near the animal’s pelvis, and are present on both males and females. The teats are vestigial but at 4cm long, they’re fairly large in comparison to the bat’s overall size. While scientists aren’t sure why the species developed the extra set of teats, or if they were functional at some point in the species evolution, the consensus is that the main purpose of the teats is to provide the pups with something extra to hang onto, making it safer to ride along with their mom during their first few weeks of life.
While studying the harem that played a central role in his paper, Bell noticed that when the female bats were spooked, they’d shift their pups to their pseudo teats before flying to the top of the roost.
Bell, Gary P. “Evidence of Harem Social System in Hipposideros caffer (Chiroptera: Hipposideridae in Zimbabwae.)” Journal of Tropical Ecology. 1987. Web. Accessed 6 November 2017. https://www.researchgate.net/profile/Gary_Bell2/publication/231882973_Evidence_of_a_harem_social_system_in_Hipposideros_caffer_Chiroptera_Hipposideridae_in_Zimbabwe/links/02e7e5370f8e4ce84c000000/Evidence-of-a-harem-social-system-in-Hipposideros-caffer-Chiroptera-Hipposideridae-in-Zimbabwe.pdf
Wright, Genevieve Spanjer “Hipposideros caffer (Chiroptera: Hipposideridae.)”
“Sundevall’s Roundleaf Bat.” Wikipedia. Web. Accessed 6 November 2017. https://en.wikipedia.org/wiki/Sundevall%27s_roundleaf_bat