Creationism in Crisis - New Thinking on How a Hunting Strategy Evolved in Barbastelle Bats - But no Comfort For Creationists.

Barbastelle, Barbastella barbastellus

Western barbastelle bat, Barbastella barbastellus

Evolutionary chance made this bat a specialist hunter - SDU

In a classic example of how scientists never take what they think they know as proven beyond question, a group of scientists led by associate professor Lasse Jakobsen of the Department of Biology, University of Southern Denmark, Odense, Denmark have reassessed how the Western barbastelle bat, Barbastella barbastellus, evolved its hunting strategy, and have concluded that the way we thought it evolved is probably wrong.

But it's no comfort to creationists because there is no suggestion that it may have been acquired by anything other than a god-free natural process or that the scientists are having any doubts about the Theory of Evolution. Indeed, the general principle of arms races is not in doubt, only whether it applies in the case of the barbastelle's hunting strategy. To add to creationist discomfort, evolutionary arms races were the subject of an early research paper by a certain Richard Dawkins together with John Richard Krebs and are now accepted as a fundamental driver of evolution. They are, of course, utterly incompatible with the notion of intelligent [sic] design.

Briefly, it was previously thought that the 'quiet' echolocation used by barbastelles to locate their insect prey was the result of an evolutionary arms race between bats and insects in which insects had evolved the ability to detect bats by their echolocation sounds and take evasive action. Bats then adjusted their sounds by either changing their frequencies or, in the case of barbastelles, turning down the volume.

Insectivorous bats use two different hunting strategies when looking for food:

1. The 'hawking strategy', in which flying insects are captured in mid-air.
2. The 'gleaning strategy', in which resting insects are taken of surfaces such as leaves.

Most of the relatives of barbastelle use the latter strategy; the Western barbastelle is unusual in the Vespertilionidae family in being a hawker. First, a little AI about the Western Barbastelle:

Please tell me all about the barbastelle bat, Barbastella barbastellus. The Barbastelle bat (Barbastella barbastellus) is a species of bat belonging to the family Vespertilionidae. This species is known for its distinctive appearance and intriguing behaviors. Here's some information about the Barbastelle bat:

Physical Description:

1. Size: Barbastelle bats are relatively small, with a wingspan of about 24-27 cm (9.4-10.6 inches) and a body length of around 4-6 cm (1.6-2.4 inches).
2. Coloration: They have dark brown to blackish fur with a paler underside. Their fur is typically quite dense.

Habitat:

1. Range: Barbastelle bats are found across parts of Europe and Asia. Their range extends from western Europe to Asia Minor.
2. Habitat: They prefer various forested habitats, including deciduous and coniferous woodlands, as well as riparian areas. These bats are known to roost in old buildings, caves, tree crevices, and rock crevices.

Behavior:

1. Nocturnal: Like most bat species, Barbastelle bats are nocturnal, meaning they are active during the night.
2. Echolocation: They use echolocation to navigate and locate prey. Their echolocation calls are relatively low in frequency and may be difficult for humans to hear.
3. Hunting: Barbastelle bats primarily feed on moths, flies, and other flying insects. They are known to hunt near water sources and often capture prey while flying low over the water's surface.
4. Roosting: They are known to roost in a variety of locations, including caves, buildings, and tree crevices. They can be solitary or form small groups.
5. Hibernation: During the winter, Barbastelle bats hibernate to conserve energy. They may hibernate in caves or other cool, sheltered locations.

Conservation Status:
The conservation status of the Barbastelle bat varies by region. In some areas, they are considered to be of "Least Concern," while in others, they are classified as "Near Threatened." Threats to their populations include habitat loss, disturbance of roosting sites, and pesticide use impacting their insect prey.

Notable Features:
Barbastelle bats have a distinctive facial appearance. They have large ears that meet at the base of the forehead, forming a "T"-shaped appearance. This unique feature helps in their echolocation and can aid in identifying the species.

Reproduction:
Barbastelle bats typically give birth to a single pup each year. Mating occurs in the late summer or early autumn, and the young are born the following summer. Female Barbastelle bats are known to use maternity roosts during the pup-rearing season.

Research and Study:
Scientists have studied the Barbastelle bat's ecology, behavior, and physiology to gain insights into their conservation needs and to better understand their role in ecosystems.

These bats play an important role in controlling insect populations, making them ecologically significant. Protecting their habitats and roosting sites is essential for their conservation and for maintaining balanced ecosystems.

The problem for the belief that barbastelles evolved a 'quiet' voice because of an evolutionary arms race has a couple of problems:

1. Most of the other bats in the Vespertilionidae family are gleaners that emit their echolocation sounds through their noses, which means they are about 20 Db lower than the hawking bats.
2. The probability that the barbastelles were ever 'loud' hawkers is thus very small, given that it evolved from a family of 'quiet' gleaners, who lack the facial morphology to emit louder sounds.
3. If they were never 'loud' hawkers, then they could not have evolved their quiet voice as part of an evolutionary arms race - which would mean evolving the necessary facial morphology, then losing it again.

So, if their quiet voice is not the result of an evolutionary arms race, where did it come from?

The answer is that barbastelles have always had it ever since the common ancestor of the Vespertilionidae evolved echolocation and adopted a gleaning hunting strategy. What the barbastelles have done is to move into a niche where insects have evolved their bat-detection ability as a result of an arms race with other hawking bats. The ability to detect flying prey without their prey detecting the barbastelle, gave them a significant advantage which the insects have yet to overcome.

It is an example of a change in the environment (bat-detecting insects) creating a niche for a species to occupy. There is no need to invoke magic or invisible designers in the process, and, to the relief no doubt, of creationists who understand the implications for their childish intelligent [sic] design notion, it is not an example of the result of an evolutionary arms race, at least in this stage of the evolution of bats. The researchers' paper in Current Biology contains more technical details. Sadly, the body of the paper is behind a paywall, but the highlights and summary sections are freely available:

Highlights

• Barbastelle bats likely evolved from a quiet gleaning ancestor
• Barbastelle echolocation reflects limitations imposed by nasal sound emission
• Stealth echolocation circumvents moth hearing but did not evolve to counter it

Summary

Predator-prey co-evolution can escalate into an evolutionary arms race. ¹ Examples of insect countermeasures to bat echolocation are well-known, ² but presumptive direct counter strategies in bats to insect anti-bat tactics are rare. The emission of very low-intensity calls by the hawking Barbastella barbastellus to circumvent high-frequency moth hearing is the most convincing countermeasure known. ^{2 ,3} However, we demonstrate that stealth echolocation did not evolve through a high-intensity aerial hawking ancestor becoming quiet as previously hypothesized ^{2 ,3 ,4} but from a gleaning ancestor transitioning into an obligate aerial hawker. Our ancestral state reconstructions show that the Plecotini ancestor likely gleaned prey using low-intensity calls typical of gleaning bats and that this ability—and associated traits—was subsequently lost in the barbastelle lineage. Barbastelles did not, however, revert to the oral, high-intensity call emission that other hawking bats use but retained the low-intensity nasal emission of closely related gleaning plecotines despite an extremely limited echolocation range. We further show that barbastelles continue to emit low-intensity calls even under adverse noise conditions and do not broaden the echolocation beam during the terminal buzz, unlike other vespertilionids attacking airborne prey. ^{5 ,6} Together, our results suggest that barbastelles’ echolocation is subject to morphological constraints prohibiting higher call amplitudes and beam broadening in the terminal buzz. We suggest that an abundance of eared prey allowed the co-opting and maintenance of low-intensity, nasal echolocation in today’s obligate hawking barbastelle and that this unique foraging behavior ⁷ persists because barbastelles remain a rare, acoustically inconspicuous predator to eared moths.

Once again then, we have an example of biologists reassessing what they thought they knew and reaching a different conclusion. No doubt to a simple-minded creationist this will look like scientists admitting they were wrong about a tiny application of a theory, so 'proving' that the entire theory, and hence the entire body of science, is wrong. So, their mummy and daddy must have been right to believe in an invisible magic sky-man designing everything by magic, 'proving' that scientifically-illiterate creationists know more than those clever scientists who think they know it all.

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