Texto de Rodrigo MedellínSamara Pérez Harp and Fer Gual Suárez 25/10/22NECTAR BATS RETURNING TO CAVE

En este texto, Fer Gual Suárez, Samara Pérez Harp y Rodrigo Medellín analizan la importancia de los murciélagos para las relaciones entre distintos países.

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Los murciélagos son los únicos mamíferos voladores y, gracias a sus manos modificadas, han logrado asentarse en todos los continentes excepto en la Antártida. Existen más de 1,400 especies en el mundo y, aunque 3 de cada 4 comen insectos, entre el resto encontramos especies que se alimentan de fruta, de peces, de carne de otros animales, de néctar de flores y más. Dentro de este grupo tan grande y diverso, únicamente tres especies se alimentan de sangre, y sólo una se ha vuelto numerosa al alimentarse del ganado introducido por el hombre. 

Gracias a estas dietas diversas, los murciélagos se convierten en nuestros aliados, cumpliendo funciones importantísimas como la polinización, el control de plagas y enfermedades y la dispersión de semillas. Y, como veremos a continuación, algunas especies migran miles de kilómetros cada año, regando estos beneficios a través de las fronteras.

Polinización transfronteriza: el murciélago magueyero menor 

Como su nombre lo indica, el murciélago magueyero menor (Leptonycteris yerbabuenae) se alimenta del néctar y polen de las flores de agaves, cactus columnares, cazahuates, ceibas y más. Estas plantas florecen en diferentes momentos a lo largo del país, a menudo en ecosistemas que son inhóspitos el resto del año. ¿La solución de los murciélagos? Migrar. Su gran capacidad de desplazamiento les permite recorrer el país entero: algunos viajan desde el centro del país hasta los desiertos del sur de Estados Unidos; otros habitan desde el sureste de México hasta Honduras. Es una coreografía precisa: los murciélagos siguen las temporadas de floración y las flores abren a tiempo para recibirlos1. Así, los murciélagos son el nexo que une a estas plantas a través del tiempo y el espacio, cargando su polen.

Murciélago magueyero menor regresando a su refugio con granos de polen de saguaro en el rostro. Fotografía: Samara Pérez Harp.

La vida itinerante de estos murciélagos les impide tener un refugio permanente para reproducirse y cuidar de sus crías. Por ello, en ciertos momentos del año, decenas de miles de madres se reúnen en unos pocos refugios con condiciones adecuadas para dar a luz. En ningún lugar sucede esto de manera más espectacular que en el desierto sonorense, donde, a lo largo de la frontera, miles de saguaros abren sus flores en mayo, justo a tiempo para recibir a las mamás murciélago a punto de parir. Ellas recorren cientos de kilómetros entre ambos países cada noche, polinizando los saguaros y regresando al refugio a alimentar a sus crías. Al final de su estancia también consumen los frutos derivados de la polinización, y año con año emprenden el largo viaje al centro de México. Así, el futuro de este espectacular paisaje transfronterizo y las especies que sostiene está ligado a las madres viajeras. ADVERTISING

Saguaro en floración en medio del desierto sonorense. Fotografía: Samara Pérez Harp.

Esta especie también está fuertemente ligada a las prósperas industrias del tequila y el mezcal. Al igual que para los grandes cactus columnares, estos murciélagos son los principales polinizadores de los agaves, llevando el polen de flor en flor a cambio de néctar. Esto ha resultado en una estrecha relación de mutuo beneficio polinizador-planta, que ha evolucionado a lo largo de más de diez millones de años. Gracias a este vínculo, los icónicos agaves han logrado prosperar y diversificarse en todo el país, dando origen a los múltiples usos que les da el ser humano. 

En los estados con denominación de origen, como Michoacán, Jalisco, Guerrero y Oaxaca, las industrias del mezcal y el tequila están valuadas conjuntamente en miles de millones de dólares. Sin embargo, en ellas se interrumpe peligrosamente la relación planta-animal, pues para convertir en alcohol el azúcar acumulado por el agave, éste debe cosecharse antes de su floración. Esto impide su reproducción sexual y priva a los murciélagos de alimento, causando que muchas hectáreas sean sembradas con hijuelos genéticamente idénticos. La importante pérdida de diversidad genética hace a las plantas menos resistentes a enfermedades, plagas y al cambio climático, poniendo en peligro a los grandes cultivos. 

Para asegurar los servicios ecosistémicos que brindan estos murciélagos y la protección de sus poblaciones, el Laboratorio de Ecología y Conservación de Vertebrados Terrestres (UNAM) creó, junto con el Tequila Interchange Project, el proyecto de tequilas y mezcales Bat Friendly©, en el que se trabaja con productores para que permitan a un porcentaje de sus agaves florecer y ser polinizados, dando alimento a los murciélagos viajeros y aumentando la diversidad genética de sus cultivos. Gracias a éste y otros esfuerzos, el murciélago magueyero menor se ha alejado de la extinción.

Control de plagas a domicilio: la migración del murciélago guanero 

En verano, en el sur de Estados Unidos y norte de México, sucede un fenómeno extraordinario: decenas de millones de murciélagos se alojan temporalmente en algunas cuevas, túneles y puentes, de donde salen nubes masivas que incluso confunden a los radares del clima. Al igual que los murciélagos magueyeros, las hembras del murciélago guanero (Tadarida brasiliensis) se reúnen al norte del país y sur de Estados Unidos a parir en inmensas colonias de maternidad. Posteriormente, pasan el invierno en grupos mucho más pequeños en el centro de México, regresando año tras año a criar a la siguiente generación.

El murciélago guanero, ícono alado de la ciudad de Austin, Texas. Fotografía: Luis A. Trujillo

Cuando el puente en Congress Avenue, a pocas cuadras del centro de Austin, Texas, fue remodelado en 1982, los ingenieros crearon —sin darse cuenta— un hogar ideal para los murciélagos. Bajo el puente, las vigas de concreto dejan ranuras oscuras, aisladas y tibias, completamente inaccesibles para los depredadores. Los murciélagos llegaron ese mismo verano y, actualmente, con aproximadamente millón y medio de individuos, es la colonia urbana de murciélagos más grande del mundo. Durante años, los periódicos locales aterrorizaron a los residentes con encabezados como “Las colonias de murciélagos devoran la ciudad” o “Terror en el aire ante la invasión de murciélagos en Austin”, mientras el gobierno recibía peticiones para erradicarlos. En 1986, Bat Conservation International llegó a la ciudad y entabló un diálogo con los tomadores de decisiones y los residentes, desmintiendo mitos y resaltando el valor que estos animales tienen para el ser humano. Hoy en día, Austin se ha convertido en la capital de los murciélagos de Norteamérica y el puente atrae a casi ciento cincuenta mil turistas cada verano a observar su salida al atardecer. ¿Qué pueden aportar estos murciélagos que logró cambiar la forma de verlos de una ciudad entera? ADVERTISING

Turistas reunidos en el puente de Congress Avenue, Austin, para observar la emblemática salida de murciélagos al atardecer. Fotografía: Elena Tena. 

Helicoverpa zea, o el gusano de los elotes, es una polilla cuyas orugas atacan cultivos de gran importancia económica como el maíz, el algodón, el arroz y el tabaco. Cada año causa pérdidas millonarias a los agricultores en toda América y el uso de toneladas de pesticidas cada vez menos efectivos. ¿Su enemigo natural número uno? Los murciélagos. 

A diferencia del murciélago magueyero, con su lengua larga que le permite extraer el néctar de las flores y polinizarlas, el murciélago guanero es un depredador formidable, que con un vuelo de hasta 160 km/h, un sistema de ecolocalización sofisticado y dientes pequeños pero afilados como dagas, puede comer decenas de insectos cada noche. Al comerse las polillas antes de que infecten a las plantas, los murciélagos retrasan el crecimiento de sus poblaciones y, por lo tanto, reducen la cantidad de pesticidas necesaria. En una región del sur de Texas se ha estimado que las mamás murciélago ahorran por año, solamente a la industria algodonera, hasta 1,725,000 dólares2Cada millón de murciélagos de esta especie consume 10 toneladas de insectos por noche. Si esto se multiplica por decenas de millones de individuos que migran a lo largo del continente, resulta en cientos de toneladas de insectos destruidas cada noche en distintas regiones, controlando sus poblaciones en beneficio del ser humano, sus cultivos y los ecosistemas. 

De costa a costa y de norte a sur: la migración del murciélago nevado

El murciélago guanero y el murciélago magueyero menor ilustran las principales razones por las que los animales migran: siguiendo su alimento, escapando de condiciones desfavorables y buscando sitios adecuados para tener a sus crías. Muchos murciélagos migran distancias menores, de los valles a los cerros, donde las temperaturas bajas les permiten hibernar. Además, machos y hembras pueden necesitar cosas distintas: ellas alimentan a las crías, por lo que migran a distintos lugares. Los hábitos nocturnos de los murciélagos dificultan el estudio de su migración y algunos, como el murciélago nevado (Lasiurus cinereus), se refugian solitariamente en árboles y arbustos y son poco comunes en toda su distribución, por lo que siguen siendo un verdadero misterio.

Los datos sugieren que el murciélago nevado migra distancias inmensas a nivel continental, desde el centro de Estados Unidos y sur de Canadá en verano, hacia las costas del sur de EU (hembras) y hasta México (machos), donde se cree que los climas más estables les permiten hibernar3. En primavera, las hembras se desplazan hacia el este, mientras que los machos se mueven hacia el noroeste de Estados Unidos y Canadá, probablemente siguiendo poblaciones abundantes de polillas, su principal alimento4. Ambos sexos aparecen en el centro de Estados Unidos en verano, cuando los bebés nacen5, y en otoño se sabe que algunos se encuentran y copulan en la costa de California.

El murciélago nevado, a pesar de ser sumamente vistoso, es difícil de estudiar debido a sus hábitos solitarios y nocturnos. Fotografía: Ganesh Marín.

Aunque el panorama no es claro, sabemos que esta especie emprende una de las migraciones más extensas y complejas entre los murciélagos. No obstante, este espectacular fenómeno está en riesgo incluso antes de que lo terminemos de entender: el murciélago nevado representa más del 30% de los cientos de miles de murciélagos que cada año mueren en accidentes con turbinas eólicas en Norteamérica. Se estima que la explosión en el desarrollo de parques eólicos en el continente podría diezmar su población a menos de la mitad para 20286. El que esto no suceda depende de que los tres países apliquen las medidas de mitigación adecuadas, permitiendo a este pequeño viajero seguir recorriendo el continente.

Los murciélagos nos conectan

La maratónica travesía que realizan las distintas especies de murciélagos migratorios año con año conecta ecosistemas a lo largo y ancho de Norteamérica y distribuye beneficios a través de las fronteras humanas. Desafortunadamente, los murciélagos son víctimas de múltiples estigmas falsos o desproporcionados que causan su persecución. Es sólo tras décadas de trabajo incansable de conservacionistas y científicos que hemos empezado a recontextualizar nuestra relación con ellos. Hoy, más que nunca, debemos ser conscientes de que las delicadas relaciones de estos animales con el resto de la naturaleza enriquecen nuestras vidas con sus dones y nos permiten disfrutar desde unos pantalones de algodón hasta un taco y, por supuesto, un mezcal. EP

  1. R. A. Burke, J. K. Frey, A. Ganguli, and K. E. Stoner, “Species distribution modelling supports ‘nectar corridor’ hypothesis for migratory nectarivorous bats and conservation of tropical dry forest,” Divers. Distrib., vol. 25, no. April, pp. 1399–1415, 2019. []
  2. C. J. Cleveland et al., “Economic value of the pest control service provided by Brazilian free-tailed bats in south-central Texas,” Front. Ecol. Environ., vol. 4, no. 5, pp. 238–243, 2006. []
  3. G. Marín et al., “Challenging hibernation limits of hoary bats: the southernmost record of Lasiurus cinereus hibernating in North America,” Mamm. Biol., vol. 101, no. 3, pp. 287–291, 2021. []
  4. E. W. Valdez and P. M. Cryan, “Food Habits of the Hoary Bat (Lasiurus cinereus) during Spring Migration through New Mexico,” Southwest. Nat., vol. 54, no. 2, pp. 195–200, 2009. []
  5. P. M. Cryan, “Seasonal Distribution of Migratory Tree Bats (Lasiurus and Lasionycteris) in North America,” J. Mammal., vol. 84, no. 2, pp. 579–593, 2003. []
  6. Friedenberg, N. A., & Frick, W. F. (2021). Assessing fatality minimization for hoary bats amid continued wind energy development. Biological Conservation, vol. 262, pp. 109309. []

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Con el inicio de la pandemia, Este País se volvió un medio 100% digital: todos nuestros contenidos se volvieron libres y abiertos.

Actualmente, México enfrenta retos urgentes que necesitan abordarse en un marco de libertades y respeto. Por ello, te pedimos apoyar nuestro trabajo para seguir abriendo espacios que fomenten el análisis y la crítica. Tu aportación nos permitirá seguir compartiendo contenido independiente y de calidad.

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It’s 7pm and I’m sitting in the bat house, rolling chair creaking on the wood floor. The bats are starting to wake up, interrupting the creak of the chair with their high-pitched chirps. I couldn’t help but smile when I learned that some bats “sing” to each other. Their social calls are interesting—less predictable than a bird call, more lively than an insect’s chirp. You probably wouldn’t notice their call in the wild unless you had heard it before. When you know what to listen for, it’s easy to hear a bat on your evening walk.

The bats chat it up in their mesh habitats (the kind of enclosure people use for butterflies, to be exact), but I can’t see most of them. They’re hiding up in the tunnels of fabric that hang from the ceiling of their habitats. You can see their outbursts, however, as they’re signaled by a vibrating piece of fabric. Some of the bats roost in baby security blankets, which are essentially a stuffed animal head attached to a small, soft blanket. These also vibrate as bats have their squabbles, a soft vibration that’s almost like a baby shaking a rattle. 

I should clarify that not all of the bat house residents are quite as talkative. The Mexican free-tailed bats are probably the most chatty, easily stirring up conversations without any kind of prompting from me. I wonder if they learned to be friendly from living in such huge colonies. It’s probably hard to be shy when you’re packed in with over a million other bats. The teeny evening bats and cave myotis have strong voices, but they’ll only use them when you have the audacity to move their roost by a whopping millimeter.

Another much quieter sound in the bat house comes from the mealworms. The mealworms wriggle in a small container, making a very soft brushing noise. I always wonder if the bats get excited when they hear it; I’m convinced that the large group of male Mexican free-tailed bats does. But then again, they seem very excited in general. 

While many of the bats prefer to stay hidden, those free-tail boys lounge right in the open. They’ll be perched on the left and right sides of the habitat, hanging from the top, clinging to the opening of the habitat. When it’s time to open their habitat, I often have to wait for Stubby, one of the older bats, to crawl off the habitat’s zippered flap so I can start pulling the many hiding spots and food dishes out one by one. 

While I’m busy corralling all the mealworms that have climbed out of the food dishes and escaped into the dark recesses of the habitat, the free-tails stare at me. They’re not bristling at the theft of what could have been a midnight snack or cowering at the huge hand that’s disrupting their evening—they’re just observing. It makes sense that these bats would be this observant when you consider what their prey is: fast-moving bugs that hide amongst the dark skies. The mealworms must seem like sitting ducks compared to the bats’ natural prey.

Many people don’t realize that bat rehabilitation often revolves around mealworm husbandry. Before I can even attempt to eavesdrop on the bats’ conversations, I have to sift through big tubs of mealworms and, well, meal. Once the mealworms are safely in a smaller, more manageable tub, it’s time to pick out the dead or over-mature ones. The worms don’t gross me out, but the grubs that are well on their way to becoming beetles are a little unpleasant. They’re the first to go.

Once the mealworms are prepped, I work my way through each of the habitats in the bat house. Most of these bats are permanent residents of the refuge, so I see the same faces each week. The bats are given many roosting options, but they pick their favorite very quickly and seem to always be in the same spot. Bats also don’t like change, and they will let you know how much you’ve disturbed them when you embark on the process of moving them from one habitat to another. 

In between cleaning habitats I go out into the flight cage. This is where releasable bats get a chance to work on their flight skills. During baby season, there are many flashes of brown, black, red, and yellow fur moving quickly through the cage. The bats do fast circuits through the flight cage, soaring over water troughs and rows of plants designed to attract moths. 

I’ll admit that the first time I was in the flight cage around sunset, I was a little anxious about having bats fly so close to me. When you see a bat flying in the wild, they’re usually far up above you. The bats in the flight cage do fly up high, but they’re close enough for me to make out their fuzzy tail membranes and broad feet. But any initial anxieties I had about being in the flight cage at night were soon calmed by seeing just how capable the bats are at flying. Even if some of the bats in the flight cage are still working on “getting their wings” and being released back into the wild, they are so adept at maneuvering in the air. They still wow me with their speed and incredible agility. They can turn on a dime, and they’re too busy having fun to want anything to do with me.

After seeing the high-flying circus acts in the flight cage, I head back to the bat house. There’s a bit more chirps than when I left because the bats have woken up a little more. When the last of the habitats is clean, all I can hear is the bats munching on their dinner (or is it breakfast?). I pack up my things, turn out the lights, and say bye to the bats. The night is young, and I know that their fun has just begun.


  Dear Lee Mackenzie,

The North American Society for Bat Research (NASBR) is saddened and moved by the long history of violence against the Black community and the systemic racism and intolerance that pervades the United States, including the role that scientists have played in perpetuating racism. We strongly condemn racism and discrimination in all forms, and we believe that science and society at large are best served when people treat each other with compassion, civility, encouragement, and mutual respect. We believe that Black lives matter. NASBR stands with our Black members, as we do with all members who are people of color. Our Society and its mission are enriched through the diversity of our members. We are committed to being better allies and advocates for all minoritized groups. However, we recognize that our Society’s membership is not reflective of the racial diversity of people in North America, and we aim to change this. Creating an inclusive, diverse, and equitable Society is part of our values, and we strive to continue moving NASBR towards this goal. To achieve this, we are establishing a fund specifically devoted to bringing Black student researchers to our annual conference. Members will provide the initial monies to create this fund, and we will seek funding from larger diversity initiatives to sustain this effort. We will continue to promote participation by people of color in our scientific and educators’ sessions. We will reserve time during our annual conferences for purposeful collaboration towards developing long-term solutions that will allow us to overcome our deficits. We acknowledge that there is much more work we need to do, and the NASBR Diversity, Equity, and Inclusion Committee and Board of Directors are eager to work with and to challenge our members to drive positive change. As always, we welcome discussion. We are listening, we will not forget, and we will do better. Sincerely, NASBR Board of Directors     www.nasbr.org


AUSTIN BATS and COVID-19:

•             Bats in Austin do not have or spread SARS-CoV-2 (the virus that causes COVID-19 in humans). SARSCoV-2 is not found in North American bat species at present.

•             Transmission of COVID-19 is from humans to other humans.

•             There are theoretical concerns about the possibility for transmission of SARS-CoV-2 from humans to bats. Research is underway; until we know more, precautions to minimize the chance of North American bats of being exposed to SARS-CoV-2 are being taken. This is not unique to bats – there are also concerns of possible transmission from humans to other wildlife species, particularly mustelids, felids and canids.

•             Avoid handling live bats and any wildlife. If handling live bats cannot be avoided, follow recommendations about PPE to prevent spread of respiratory droplets – a face mask, thick gloves, etc.

  •              The concern is transmission of SARS-CoV-2 from humans to bats, not vice versa, so handling dead bats is fine. Dead bats provide valuable information to bat biologists. To collect a dead bat, wear gloves, wrap in paper towel, and double bag in a Ziploc. Place on ice or in freezer until the bat can be retrieved. Avoid any skin contact to prevent rabies exposure and keep pets and children away.

Bat conservation and COVID-19

•             Many bat species have adapted to urban and rural environments, where they coexist safely with people. Ask us about living with bats safely.

•             It is important that bats and bat habitat not be destroyed because of unfounded fears over coronavirus transmission.

•             Bats in North America are in trouble from habitat loss and white-nose syndrome – at least two species in Texas have experienced sharp decline just this spring.

•             Bats are essential to our Texas ecosystems and economy. Nationwide, bats are estimated to provide $23 billion of natural pest control each year.

•             Killing bats would not have any effect on the spread of COVID-19, but would negatively affect bat populations, conservation efforts, and our economy.

Austin Bat Refuge would like to remind people we are here to answer your questions and collect reports on bat sightings, bat roosts, and dead bats.  Contact us at info@austinbatrefuge.org and 512-695-4116 or 512-799-8847.

(This post borrowed and modified from BC Community Bat Program)


Article published in Global Bat Net

Posted: 20 Apr 2020 09:31 AM PDT

Contributed by: Melissa Ingala & Ariadna Morales

            Many people are under the impression that all bats carry diseases that could pose threats to humans. This concern has recently increased because a virus hosted by one bat species seems to be a distant relative of SARS-CoV2. There have been many studies suggesting that because of their ability to fly, unique immune systems, and colonial nature, bats are special reservoirs for zoonotic pathogens— organisms that cause disease and are naturally transmitted between animals and humans. However, a recent study showed that when we account for species richness (i.e. the number of species in an evolutionary group), bats are no more likely to transmit zoonotic viruses than other groups of mammals. In other words, it is likely there are many viruses hosted by bats simply because there are many species of bats, not because they are more inherently dangerous to humans than other groups of mammals. Although this may not sound very comforting given that the world is dealing with a deadly virus, killing bats is not the solution to preventing outbreaks of zoonotic diseases.

Can we prevent a future outbreak by reducing bat populations that might host viruses? There is no evidence that bat culls prevent or diminish disease transmission. In fact, we might produce the opposite effect. For example, attempts to reduce vampire bat colonies in Peru resulted in higher rabies transmission in the bats left behind because culls skewed populations towards juveniles (which are more likely to transmit rabies). Similarly, putting bats in peril of extinction may further increase the number of viruses they can host. Some bats considered Near Threatened or Vulnerable by the International Union for the Conservation of Nature (IUCN) had higher viral richness than bats considered of Least Concern. Based on all currently available evidence, killing bats does not have any benefit for disease management. 

Headshot of a striped Keenan’s bat (Gardnerycteris keenani), a South and Central American species that feeds on insects (left). Pallas’s long-tongued bat (Glossophaga soricina), a South and Central American species that feeds on nectar, such as that of the banana flower in the photo (right). Photos by Sherri & Brock Fenton.

Bats provide more benefits to our everyday lives than we can imagine, and decreasing their populations would have rippling effects on agriculture and natural ecosystems. Bats provide millions of dollars in free pest control services all over the world and pollinate many plants cultivated by humans, including tequila agaves, mangos, and durians. Bats can also help us in the fight against global deforestation and climate change by dispersing seeds and helping to regenerate the rainforests. Losing bats would hurt humans more than it could ever protect us, so in order to protect ourselves, we need to realize the value of protecting bats.

So how can we prevent new pathogen spillovers from bats to humans? Part of the answer lies in changing our own behaviors and the ways we interact with the natural world. One way we can change behaviors is by providing people with accurate, consistent information about avoiding contact with disease reservoirs. Since all vertebrates naturally host viruses and bacteria, avoiding situations where pathogens might be amplified or transferred is most important. In the case of hantavirus, a serious respiratory illness transmitted by rodents, disease transmission has been curbed through educational outreach encouraging people to avoid rodent urine and refrain from sweeping in areas with rodent droppings, since sweeping causes viral particles to become airborne. The number of viruses circulating in bat populations may even be influenced by outside factors including many human activities. For example, deforestation and the presence of humans in Western and Central Africa have been linked to the occurrence of fruit bats that tested positive for Ebola virus antibodies. These regions overlap with known Ebola outbreak areas, suggesting that the more humans encroach on bat habitats, the higher the risk for viral spillovers. To prevent the next pandemic, we need to take decisive action to stop encroaching on wild spaces and protect more lands and habitats.  Actions forming and preserving natural and artificial buffers between humans and wildlife will be critical to protecting human health as well as wildlife health.


04/09/2020
Merlin D. Tuttle

I am writing in response to the unprecedented situation now presented by COVID-19 in North America. Early suggestions regarding potential transmission of SARS-CoV2 from humans to bats have raised serious concerns among research colleagues, rehabilitators, and cavers. In perusing available knowledge, I agree with veterinarian, Renee Schott. She has pointed out that we can’t control the public and their interactions with bats. Also, she notes that “COVID is everywhere in the U.S. right now. If North American bats can get it, they will get it.” She further warns that inappropriate restrictions could hasten the spread.

I sympathize with federal and state agencies who will be expected to take protective actions. Nevertheless, premature action could prove worse than none at all. SARS-CoV2 is already present worldwide, and bats appear highly resistant to coronaviruses. We seem to be considering rather serious actions to ward off threats not yet proven to exist and that may have serious unintended consequences.

Researchers unable to rapidly comply with new restrictions are already facing costly disruptions and termination of projects essential to conservation. Rehabilitators, forbidden to further assist bats, are reporting high-risk public actions. How would caving restrictions be enforced in state and federally managed tour caves, for example at Mammoth Cave or Carlsbad? And how could long-term restrictions on public access to other caves be enforced? What are the potential consequences of frightening the public with hypothesized disease transmission from mere breathing?

When faced with the choice of protecting bat benefits versus one’s family from potential death, the outcome is clear. Public overreaction to hypothetical threats of disease from bat droppings, or even bat breath, could prove disastrous, leading to intolerance and widespread killing of bats. Media speculation has already caused harm that may last for decades.

Regardless of presence in bats, new COVID strains in humans and other animals likely will appear. State and federal agencies, who have a responsibility to protect wildlife, cannot stop all interactions with wildlife, and bats are far from the only animals that can contract COVID. It’s already in cats and dogs.

As veterinarian, John Huckabee, has suggested for bat rehabilitators, the watchful eyes of researchers and cavers could prove invaluable, both in protecting bats from fearful humans and in providing early surveillance. We can only hope that government decision makers will consider the Hippocratic oath—first do no harm.

For further information on the COVID-19 pandemic and how it relates to bats, please read my editorial “A Viral Witch Hunt” published in the March 27 edition of Issues in Science and Technology.


Flying foxes are dying en masse in Australia’s extreme heat

In three days before Christmas, thousands of the mammals died in 110-degree heat in one Melbourne park.

Dozens of panting, suffocating gray-headed flying foxes clump together in an attempt to survive 110-degree heat in Yarra Bend Park, outside of Melbourne, in late December. Some 4,500 foxes, including many of these seen here, died over three days in the park.

Photograph by Doug Gimesy

By Natasha Daly

PUBLISHED January 7, 2020

The 30,000 gray-headed flying foxes in Yarra Bend Park, just outside the heart of Melbourne, Australia, were having a fairly normal early spring.

In September and October—springtime in Australia and prime birthing season for the 11-inch long megabats—many of the flying foxes had returned to the park from their winter migration

up the coast. Females were birthing pups as normal, says biologist Stephen Brend, who is in charge of monitoring gray-headed flying foxes in Victoria province, including at Yarra Bend Park, which is home to a significant colony of the bats. All was routine.

“And then the horror started,” Brend says. “It got too hot, too quickly.”

Incapable of surviving the extreme, relentless heat that gripped Melbourne in December, the flying foxes were dying. Across three days just before Christmas, when temperatues exceeded 110 degrees Fahrenehit, 4,500 of the park’s gray-headed flying foxes perished—15 percent of the colony’s population.

The tragedy for flying foxes in the park echoes scenes of wildlife suffering across the country and puts a spotlight on the perils of extreme heat, which for some species can be just as deadly as fire. Great and small, fast and slow, Australia’s endemic animals are falling victim to the heatwaves and fires that are ravaging the country at an unprecedented scale. It’s the hottest and driest summer in Australia in recorded history. As the planet warms, large-scale fires are becoming more frequent, and bushfire seasons are getting longer.

For gray-headed flying foxes, which are classified as vulnerable to extinction by the International Union for the Conservation of Nature, the Yarra Bend event is not isolated. “The colony in Adelaide suffered even worse,” says Brend. Several thousand flying fox babies died there from extreme heat between November and January, says Justin Welbergen, associate professor of animal ecology at Western Sydney University and president of the Australasian Bat Society. On January 4, many thousands of flying fox babies died across multiple roosts in and around the Sydney region in New South Wales, where the temperature reached a record-breaking 121 degrees Fahrenheit. Welbergen’s team, which monitors flying fox heat stress conditions, is calculating a final death toll.

This summer’s extreme heat and extreme fires, which have imperiled Australia’s entire eastern coast—prime flying-fox habitat—“risk wiping out the 2019 generation” of newborn bats, Brend says. Some 80 percent of flying fox pups are born in October. They were young and vulnerable when heat waves and wildfires broke out late last year.

Hour by hour in extreme heat

A day in the life of a flying fox in a heatwave is unforgiving. By 5:30 a.m., as dawn breaks, the bats have returned to their trees after spending the night feeding on nectar and fruit. By 8 a.m., Brend says, it’s getting hot in their roosts. The bats fan their wings to keep cool, but they can only do it for so long before they start to get tired, he says. By noon, they’re getting exhausted, and temperatures continue to climb. The bats start to pant, which accelerates dehydration.

At that point, they could fly into the river to get a drink (the Yarra River runs through the middle of the 640-acre park), “but it’s like us running to the shop in the middle of a heat wave,” Brend says. Flying takes energy, and when they’re exhausted and dehydrated, they’ll simply stay put.

Distressed and starting to panic, the bats try to find a cool spot. Mothers will deposit their babies on branches and separate, Brend says, searching for a tree trunk that might be cooler. The bats follow each other—spotting one on a trunk seems to signal to the rest that it’s a refuge. They start to clump together. “It’s like a football scrum of bats,” Brend says. “To the observer, it looks mindless.” The ones who got there first are now surrounded and smothered by dozens of others.

“At that point in time everything has gone wrong,” Brend says. That’s when his team, made up of park staff and volunteers, will step in to try to break up the clumps by spraying them with water, which cools them down and slakes their thirst.

Tragedy on the trees

On December 20th, at the height of the three-day heat event that killed 4,500 flying foxes, “it never got cool,” Brend says. At 9 p.m., the team was out spraying. But it was pitch black, tree limbs were falling, and there are venomous snakes in the brush. “We had to call it off. We couldn’t see. It was 38 degrees [100 degrees Fahrenheit]. It was deeply distressing,” he says. “It was carnage.”

“One falls, and the rest cascade on the ground, crushing and suffocating each other. Dozens if not hundreds of dead or dying bats are at the bottom of the tree,” says Melbourne-based photojournalist Douglas Gimesy, who documented the December rescue efforts. “You’re looking down at them and they’re looking up at you gasping. They’re smothering and heating up. Volunteers will go in and separate out bodies and find some that are still alive. But you’ve got 20 to 30 rescuers and 4,500 bats. It’s like a war zone. It’s sad and distressing and heartbreaking, and you know it will happen again and again and again.”

“Some we get to in time,” says Tamsyn Hogarth, one of the rescuers. “Others die in your hand.” By the third day, on December 20th, the air was thick with “the smell of death,” she says. Hogarth runs Fly By Night, a wildlife shelter in Melbourne dedicated to rescuing, rehabilitating, and releasing gray-headed flying foxes. She and other volunteers rescued 255 babies during the extreme heat events in December in Yarra Bend Park. Two dozen volunteers across Victoria province are currently caring for the bats, which range in age from two to 12 weeks old.

Heatwave deaths are normal for the bats—but this is different.

Hot days causing bat deaths are normal in Yarra Bend Park. “We’re always worried about heat events. You’re not going to get through summer without having really hot days,” says Brend.

Last summer, for example, a few hundred bats died, he says.

One study found that between 1994 and 2007, approximately 30,000 gray-headed flying foxes died in extreme heat events in Australia.

But the timing of this year’s extreme heat—right after birthing season—contributed to unusually high mortality. Because the young were still nursing, their mothers’ energy levels were depleted, and all of them—parents and new babies—are more vulnerable, Brend says. The first weekend in December was extremely hot, and it was followed by a succession of hot days all month, culminating in the three-day death event, reaching a peak of 110 degrees Fahrenheit in Yarra Bend on December 20.

“It’s emotional and frightening for the species. And this is happening across their entire range,” Brend says. While Yarra Bend Park hasn’t been hit by fires, much of the flying foxes’ habitat lies directly in the fire zones along Australia’s east coast.

A modern-day passenger pigeon?

A May 2019 national survey estimated that there are around 589,000 gray-headed flying foxes in Australia. Although their numbers are robust now, they face a host of threats, from routine extreme heat events to entanglement in urban infrastructure, such as nets and barbed wire, as well as harassment from residents who see them as pests.

The bats are nomadic. Much of their range is currently in the fire zones. Many travel north in winter, roosting in forests along the coast, which they may find scorched. The “bushfires have destroyed essential foraging resources on unprecedented scales,” says Welbergen. “There is no refuge for them,” says Brend. “It’s not like it’s bad in Melbourne but will be OK in northern New South Wales—it’s not OK anywhere.”

“That can’t go on for too many cycles before the population declines,” Brend says. “I don’t want to be alarmist or dramatic—there are still thousands of these bats—but there’s no reason to be confident anymore.”

“Our worry is we’ll have the new passenger pigeon,” he says, referring to what was once the most abundant bird in North America before being hunted to extinction in the 19th century.

‘Bats need the forest and the forest needs the bats’

Flying foxes play a vital role in the forest. “Their ecological role is as big, nocturnal bees,” Brend says. They carry seeds and pollinate trees, gardening the forest by night. “Bats need the forest and the forest needs the bats,” says Brend.

And it’s still the middle of summer in Australia. “We’ll battle on for our upside down friends,” says Lawrence Pope, a rescuer caring for five orphaned baby bats at home, “but things look very grim.”

“In this horror year, all species are suffering. It’s really frightening,” Brend says. “We’re hot, and they’re hot, and it’s a nightmare.”


Just back from the 49th Annual Symposium of the North American Society for Bat Research in Kalamazoo, Michigan and what a treat it was!

There’s nothing better than being in a room full of passionate, brilliant people, sharing their hard-won knowledge for the benefit of bats around the world. It is, however, much like drinking from a fire-hose, with a new presentation of cutting-edge research every 15 minutes for three days.

Highlights included a photography workshop led by the legendary Brock Fenton & Merlin Tuttle, and up-and-coming Price Sewell.
Rodrigo Medellin presented fascinating work on the second-largest bat in the Americas, the Wooly False Vampire bat, showing that this carnivorous bat requires large, well-preserved forests for its conservation.

We really enjoyed talking to the many undergrads who explained their posters describing results of their fieldwork.

But mostly we were happy to catch up with old friends and make new ones, while discussing the latest efforts to mitigate threats to bats, including WNS, wind turbines, and habitat loss.

On the way back home, we got to wait for a delayed flight with Texas State Mammalogist Jonah Evans, who in addition to leading state efforts to fight WNS, also found time to entertain with his guitar till 1:30 am the previous night in his hotel room. What a good dude!