Student Feature: Bats

U of A PhD student Simon Tye recently visited the University of Arkansas Museum’s zoology collection to examine bat specimens from Arkansas. In this blog post, he delves into how museum natural history collections can be significant resources for understanding the past, present, and future of bats and other animals facing conservation concerns.

Zoological Collection: Bats

University of Arkansas Museum

Simon Tye, PhD Student, Siepielski Lab, University of Arkansas

Origin of Zoology Collections

Humans have examined and preserved plants, animals, and other organisms for millennia. Over time, our growing knowledge of biodiversity led us to collect and catalog natural history information about particular species. Initially, information about different animal species was typically acquired by observational techniques or by capturing, euthanizing, and preserving specimens from different localities. These specimens were then deposited into regional, national, or international museums where they were properly maintained for years to come. Using museum collections, researchers were then able to conduct in-depth comparisons of different species and different individuals within the same species. Eventually, comparisons of external and internal traits (i.e., morphology) among different species were compiled into lists, known as dichotomous keys (Fig. 1).

These keys are still used by many researchers today to distinguish species in the field and the laboratory. In addition, the location and habitat data of museum specimens were compiled to create species distribution maps that show where particular species occur.

Figure 1. Example of a dichotomous key for bats of the United States¹. Dichotomous keys provide frameworks to help determine the identify of particular species by comparing diagnostic traits, or traits that differ between species. After answering the first question about a particular trait (e.g., 1. Nose leaf…), researchers proceed to the next recommended question(s) (e.g., 2. Tail present…) until they identify the species.

The original purposes of zoology collections have provided modern researchers many additional opportunities to learn about particular species and groups of organisms. First, by comparing different individuals of a species that were acquired across their distribution (Fig. 2), researchers may examine how morphological traits vary across habitats². Second, by comparing individuals from a particular population (i.e., a group of interbreeding individuals), researchers may learn about fine-scale levels of diversity among different individuals³. Third, by accumulating these comparisons over time, researchers may coarsely examine the recent evolutionary histories of particular species⁴. Lastly, researchers are now able to acquire genetic material from some museum specimens to learn about the underlying mechanics of observed and unobserved changes over time⁵.

Figure 2. Indiana bats (Myotis sodalis) at the University of Arkansas Museum. These historical specimens were collected before the species was listed as endangered and provide opportunities to study an imperiled species that inhabits woodlands near Fayetteville, AR.

Bats of Arkansas

To highlight the importance of historical and contemporary museum specimens, I am going to discuss the bat collection at the University of Arkansas Museum (Fig. 3) and the pertinence of modern bat specimens. There are over 1,300 known bat species, which represents about 20% of all mammal species on the planet⁶. At least 51 bat species occur in the United States⁷, 16 of which are known to inhabit parts of Arkansas. The bat collection at the University of Arkansas contains 14 of the 16 species known to inhabit the state, two species that occur elsewhere in the United States, and two species from Asia.

Bats are of particular concern in United States due to widespread population declines caused by white-nose syndrome⁸, anthropogenic developments⁹, and climate change¹⁰. For example, of the 16 bat species that inhabit Arkansas, three are listed as endangered and one is listed as threatened under the Endangered Species Act. However, it should be noted that, for many species around the world, there are differences amongst federal and international designations. For example, the northern long-eared bat (Myotis septentrionalis) is considered endangered in Canada, threatened in the United States, and near threatened by the International Union for Conservation of Nature and Natural Resources (IUCN). These discrepancies are largely because of bureaucratic roadblocks and the extent to which a species distribution is in a country. . Importantly, the acquisition and collection of zoology specimens is heavily regulated by state and federal laws and regulations such that a justification, euthanasia technique, and specimen quantity must be approved prior to collection.

Figure 3. Fourteen of sixteen bat species that are known to inhabit Arkansas. Five of these species are considered of concern, vulnerable, threatened, or endangered by various federal laws and organization designations. Location data for these species have been removed for their protection.

Modern Zoology Collections

Truth be told, collecting and depositing specimens in museums has become increasingly uncommon. This is due, in part, to our perceived level of knowledge about the distributions and morphologies of particular species.

Yet many species distributions are shifting, expanding, and contracting due to combined effects of habitat loss and fragmentation, climate change, and other anthropogenic disturbances¹¹. For example, the draining and channelization of waterways (i.e., dams, diversions, canals) across the Great Plains has led to the proliferation of woody vegetation in riparian corridors¹⁴. In addition, the hinderance of natural wildfires has allowed woody vegetation, particularly eastern red cedars (Juniperus virginiana), to thrive in once treeless grasslands. In turn, these environmental changes have created a safe corridor for some woodland species to travel across expansive, treeless environments between the Rocky Mountains and woodlands of the eastern United States¹⁵.

In addition, we are beginning to find some cryptic species – distinct species that was previously undetected because their morphology is nearly identical to another species¹². In some cases, cryptic species have been revealed by using modern genetic techniques on historical museum specimens. For example, genetic data suggests that two species of crocodiles inhabit the Nile River, whereas we previously thought only one species inhabited the river valley¹³. These findings are important because they have shown that, while one crocodile species is abundant, the other species is increasingly rare¹³. Due to these tendencies, the proper maintenance of museum collections is vital to understanding the biological world during a period of drastic global change.

Figure 4. Representative photos of different bats species. The two species on the left occur in Arkansas, whereas the two species on the right are very similar to species that occur in the state. The species, clockwise from the upper left, are a female hoary bat (Aeorestes cinereus) with two juveniles, a Townsend’s big-eared bat (Corynorhinus townsendii), a western red bat (Lasirurs blossevillii), and a silver-haired bat (Lasionycteris noctivagans).

Species Distributions

By now, you’re probably wondering how this information relates to bats. A few years ago, I was a research technician in southwestern New Mexico. Each night, our team would catch bats and attach radio-transmitters (small geolocation devices) to particular bat species. By doing so, we could locate bat roosts and inform researchers and conservationists about what habitats to conserve for the persistence of these species¹⁶.

The year before I was a technician, the other team members unexpectedly captured an evening bat (Nycticeius humeralis)¹⁷. While this may seem uneventful, historical records suggested that this bat species inhabited the eastern United States. In fact, this individual was about 300 miles away from the closest known locality (Fig. 5). For now, this isolated observation may simply represent an individual that wandered outside of their known species distribution. However, repeated observations of evening bats in the southwestern United States may reveal that there are viable populations in this region. For example, repeated captures of eastern pipistrelle (Pipistrellus subflavus), another bat species that historically inhabited the eastern United States, have shown that their distribution is expanding into the western United States¹⁸. Thus, due to the scientific importance of these and similar observations, as well as the relatively stable population levels of these particular species, these specimens were properly documented and deposited in a regional museum.

Figure 5. Species distribution of the evening bat (Nycticeius humeralis)¹⁷. Different shades of gray represent updated distributions based on recently collected specimens^17,19,20. The individual that was captured in southwestern New Mexico (open circle) was about 300 miles from the closest known locality in southwestern Texas.

Species Identification

Importantly, revealing these trends depends upon the reliability of historical museum specimens. As previously mentioned, in some instances, we have learned additional information about what differentiates particular species and need to re-evaluate historical specimens. For example, Dr. Keith Geluso, a professor at the University of Nebraska at Kearney, has re-examined museum specimens of western red bats (Lasiurus blossevillii) across the southwestern United States. Historically, it was thought that western red bats and eastern red bats (L. borealis) had relatively disjunct distributions, such that western red bats and eastern red bats occurred in the western and eastern United States, respectively. However, Dr. Geluso has found that some historical specimens of western red bats obtained in the southwestern United States were misidentified and are actually eastern red bats. This finding is important because it suggests that: 1) the species distributions of western and eastern red bats overlapped more than previously thought, and 2) modern bat researchers in the western United States need to thoroughly identify captured bats instead of assuming historical distributions are foolproof.

The Future of Zoology Collections

Lastly, I want to briefly emphasize the importance of these collections in our rapidly changing world. As mentioned above, many bat populations are experiencing substantial population declines across the eastern United States⁸. In addition, the spread of white-nose syndrome in the western United States has placed the future of bat populations in the United States in perilous territory. To help combat the spread of white-nose syndrome and limit human transmission, bat researchers across the United States use personal protective gear and sterile equipment when capturing bats. In addition, citizens across the country have built small bat houses to help populations persist through this tumultuous time. Lastly, there are several promising techniques being developed to combat white-nose syndrome, such as UV radiation treatments that eradicate the fungal pathogen that causes the syndrome²¹. While much damage has already been done to bat populations across the country, these precautions, community initiatives, and techniques may help save some remaining bat populations from future fungal contaminations.

Regardless of the future of Earth’s biodiversity, the foresight of our ancestors has provided historical museum specimens for generations of scientists to compare and contrast. Unfortunately, fewer and fewer specimens are being added to museum collections²² during the most environmentally turbulent time in recent history²³. In actuality, this is one of the most important time periods for specimens to be collected because these specimens provide vital information about how species are affected by drastic environmental changes²⁴. These notions are further confounded by the ethics of collecting specimens when extinction rates are occurring at a faster rate than at any point in human history²⁵. To clarify, I am not advocating for the haphazard euthanasia of animals; I am advocating for the proper continuation of an important practice in biological research when it is deemed scientifically necessary. So long as natural history information – the foundation of modern biological research – is valued by academic communities and the general public, the proper collection of zoology specimens will provide biologists with opportunities to unearth vital information about the mechanisms and processes that dictate life as we know it.

References

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