Figure 1. The false vampire bat hovering before attacking a mouse in dry fallen leaves, listening to locate is prey in accord with a hypothesis of bat origins first presented here. The first pre-bats were not as adept at falling on prey, but refinements followed.
Earlier we looked at a new hypothesis for bat origins
that separated the distance gliding origins of small-hand colugos from the accurate falling, flapping origin of big-hand bats. Today readers get to see a video (below, Figs. 1, 2) showing that ancient and original behavior – still retained by the carnivorous wooly false vampire bat (genus: Chrotopterus). This may not be the most primitive extant bat, but this video demonstrates the predatory behavior that led to the origin of bats:
- inverted hanging >
- falling on prey while flapping to brake its descent >
- covering the prey item with ankle-to-hand membranes >
- capturing the prey item with its mouth >
- leaving the scene of the attack with prey in tow to feed later.
Figure 2. Scenes from the video showing the stages in the bat attack on the mouse in the leaf litter. Note how the former nursery membrane, now a flight membrane, covers the prey, preventing its escape.
Click the video to view it.
Before bats had sonar
bats relied on rustling sounds in the leaf litter to find their rodent and insect prey. Gradually refining this ability is what led to sonar in micro bats.
Before bats could fly
inverted pre-bats fell from tree limbs, flapping their small hands to slow their inevitable descent. Gradually refining this ability, while gradually enlarging those big membraned bat hands is what led to slowing the decent, hovering prior to the attack and ultimately flying and chasing flying insect prey.
This bat origin hypothesis
solves the problem of bat flapping without display (as in theropods and fenestrasaurs) and without WAIR (wing-assisted inclined running, as in theropods and fenestrasaurs). Remember bats have very weak and rotated backwards hind feet. Bipeds they were, but inverted and non-cursorial, distinct from pterosaurs and birds.
Remember
colugos, bats and basal pangolins, like Zhangheotherium, were members of the clade Volitantia. This placental clade is close to metatherian stem placentals, like Monodelphis, that have ventrally open pouches. These pouches were originally to protect nursing underdeveloped newborns, then expanded to form nursery membranes, then further expanded and co-opted for gliding in colugos and flying in bats.
How wonderful
that some bats retain their original and ancient method of hunting, as shown in the video. So many times in paleo, the answer has been staring at us, out in the open, waiting for recognition. On that note, I have sent emails to several leading bat experts, referring them to the earlier blogpost on bat origins, asking for their feedback. None, so far, have responded.
References
photographer: Anand Varma
The Pterosaur Heresies 