This blog post was originally published by Columbia Science Review in November 2013.
By Alexandra L. DeCandia
The situation may be worse than we anticipated for the little brown bat (Myotis lucifugus). In a new study published by University of Illinois researchers earlier this week, it appears that the fungus Pseudogymnoascus (Geomyces) destructans (the cause of White-Nose Syndrome or WNS in bats) is even more resilient than previously thought. Able to colonize any complex carbon source found within the confines of a cave environment, the fungus can persist on a numerous organisms and at a variety of pH levels. For the little brown bat, this implies that any attempt at the fungus’ eradication from known hibernacula proves futile. The fungus will merely lay in wait on another organism until its preferred host reappears en masse each fall.
The North American strain of Pseudogymnoascus destructans (Gd) examined in this study first appeared in 2006. Infecting only a few hibernacula in upstate New York, the fungus has since spread to over two-dozen states and migrated as far northward as Canada. Highly transmissible, highly persistent, and incredibly lethal, Gd has already claimed the lives of over 5.7 million North American bats with no perceivable end to its destructive reign yet in sight.
Gd infects bats while they hibernate, passing from one individual to the next in the cramped conditions of a M. lucifugus colony. The fungus grows on the cold cutaneous tissues of their muzzles and wings and specifically degrades their epidermal keratin. Resultant lesions form and increase the bat’s vulnerability to other pathogens and parasites lurking within the caves.
Of even greater concern, though, is the fungus’ effect on the patterning of torpor and consciousness during hibernation. As an order, chiropterans possess incredibly efficient metabolisms. Flying or even heating their bodies above ambient temperature can deplete their energy stores to the point of emaciation within days. Therefore, remaining in a state of torpor (i.e. decreased body temperature, lowered metabolic rate, etc.) proves crucial when ambient temperature and food availability decrease in winter. Bats infected with Gd cannot remain in hibernation undisturbed, due either to fungal itch or rapid dehydration. With increasing frequency, they arouse until ultimately perishing from starvation.
Intrinsic value of the species aside, the loss of so many little brown bats at the hands of Gd-induced starvation poses a serious economic risk to North Americans. Through insect predation, consequential reduction in pesticide utilization, and natural agricultural pollination, bats provide ecosystem services worth an estimated $3.7 to $53 billion USD per annum (Boyles et al., 2011). Should WNS eradicate certain chiropterans from the continent as it seems poised to do (at least as far as M. lucifugus is concerned), thousands of metric tons of insects will pour into our fields and lead to a cascade of negative ecological, economic, and human health implications.
Combatting Gd and WNS has proven difficult thus far, to say the least. Studies have concluded that even if little brown bats manage to evolve means of surviving infection (as their European cousins have done), their populations will still decrease to fewer than 1% of their initial numbers within 20 years (Frick et al., 2010). Such estimates combined with the newfound resilience of Gd paint a grim depiction of the future for M. lucifugus, but they by no means necessitate surrender. Scientists continue to seek physical, chemical, and biological means of impeding the fungus, and some have even developed artificial hibernacula devoid of spores for bats to roost in unaffected. While neither management strategy has yet proven to drastically mitigate the spread of WNS, they represent steps in the right direction towards preserving an often overlooked but economically and intrinsically significant species, North America’s little brown bat.
This blog post was originally published by Columbia Science Review in October 2013.
By Alexandra L. DeCandia
With an ever-increasing frequency, one pudgy little marsupial is making headlines. Proclaimed the “Happiest Animal in the World” by Huffington Post some ten months ago, the quokka has since bundled into millions of hearts with its teddy-bear frame, cheeky grin, and characteristically social nature. Despite its near constant appearance on internet forums such as BuzzFeed and Reddit’s r/Aww, public awareness of the modern risks to quokka populations remains low.
Quokkas are one of the many species listed as vulnerable on IUCN’s Redlist (a wildlife conservation database). Due to their extreme endemism in the southwest corner of Australia and its two abutting islands (Rottnest and Bald), quokkas are particularly sensitive to habitat fragmentation, destruction, and climatic alteration. Unfortunately, as a result of human activities, quokka populations now face all three such threats. In fact, in a study conducted by Lesley Gibson et al. (2010), extinction is estimated to occur as early as 2070 if steps aren’t taken to drastically mitigate the species’ decline.
In order to combat threats afflicting native species, it is crucial for scientists to understand the exact causes of projected population declines. For quokkas, these causes are directly linked to their preferred habitats. In Australia, a continent marked by deserts and aridity, quokkas thrive as vegetative specialists. Nocturnal foragers, these herbivorous wallaby-relatives seek dense, shrubbery-laden habitats near swamps to permanently lodge their societies of 25-150 individuals. Historically, these habitats occurred in regions with 700 mm of annual rainfall. However, recent quokka populations have shifted to reside in areas receiving over 1000 mm of rain per annum as a defense mechanism. Small and ill-equipped to fend off predators with their chubby cheeks and tiny paws, quokkas rely on rain-fed vegetation for protection as well as nutrition. Seeking ample rainfall in an arid locale may not seem a winning strategy, but it is one that has obscured quokkas from dingoes, foxes, cats, and even large birds for millions of years. As humans alter the environment in unprecedented ways, though, the quokka’s strategy may no longer apply.
Foremost among risks to quokkas lies climate change. With the continued outpouring of anthropogenic greenhouse gases into the atmosphere, the overall temperature of our planet is increasing. For some areas, such as the northeastern United States, climate change will bring wetter conditions and more frequent occurrences of super-storms. For others, such as the entire continent of Australia, climate change spells increased heat-indices and ultimate desertification. Even the mildest models examining these rainfall alterations and projected quokka distributions predict ultimate range restriction. The most extreme models foresee extinction within our lifetime. Without dense vegetation afforded by ample rainfall, quokkas will be unable to defend against natural and introduced predators. Ultimately, they will be hunted to extinction as desert and suburbia afford little protection.
However, despite the gloom-and-doom nature of this Holocene Extinction, there exists hope for the quokka moving forward. In the best-case scenario, mankind can halt climate change, eradicate introduced predators, reconnect fragmented habitats, and expand the quokka’s current range to encompass greater (and wetter) regions. In a more realistic scenario, man can limit further greenhouse gas emissions, control invasive predator populations, conserve existing habitat, and design an action plan for species relocation should their current range ultimately disappear. The bottom line is that quokkas do not have to die. Steps can be taken towards their protection.
The quokka is just one species currently staring at the face of extinction. As human populations continue to grow at astronomical rates, it becomes our duty protect those we have harmed in our meteoric rise. Studying the effects of climate change on endemic species and managing their recovery programs before their necessary institution is and should be our present reality. Otherwise, we risk the loss of those species that make this planet worth the fight. Otherwise, we risk the loss of that contagious smile of the world’s happiest animal.
This page links to blog posts I've written about wildlife conservation and the environment. Please see linked websites for original versions.