Barotrauma is a significant cause of bat fatalities at wind turbines

SummaryBird fatalities at some wind energy facilities around the world have been documented for decades, but the issue of bat fatalities at such facilities — primarily involving migratory species during autumn migration — has been raised relatively recently [1,2]. Given that echolocating bats detect moving objects better than stationary ones [3], their relatively high fatality rate is perplexing, and numerous explanations have been proposed [1]. The decompression hypothesis proposes that bats are killed by barotrauma caused by rapid air-pressure reduction near moving turbine blades [1,4,5]. Barotrauma involves tissue damage to air-containing structures caused by rapid or excessive pressure change; pulmonary barotrauma is lung damage due to expansion of air in the lungs that is not accommodated by exhalation. We report here the first evidence that barotrauma is the cause of death in a high proportion of bats found at wind energy facilities. We found that 90% of bat fatalities involved internal haemorrhaging consistent with barotrauma, and that direct contact with turbine blades only accounted for about half of the fatalities. Air pressure change at turbine blades is an undetectable hazard and helps explain high bat fatality rates. We suggest that one reason why there are fewer bird than bat fatalities is that the unique respiratory anatomy of birds is less susceptible to barotrauma than that of mammals

Impacts of wind energy development on bats : A global perspective

Wind energy continues to be one of the fastest growing renewable energy sources under development, and while representing a clean energy source, it is not environmentally neutral. Large numbers of bats are being killed at utility-scale wind energy facilities worldwide, raising concern about cumulative impacts of wind energy development on bat populations. We discuss our current state of knowledge on patterns of bat fatalities at wind facilities, estimates of fatalities, mitigation efforts, and policy and conservation implications. Given the magnitude and extent of fatalities of bats worldwide, the conservation implications of understanding and mitigating bat fatalities at wind energy facilities are critically important and should be proactive and based on science rather than being reactive and arbitrary

Evidence of late-summer mating readiness and early sexual maturation in migratory tree-roosting bats found dead at wind turbines

Understanding animal mating systems is an important component of their conservation, yet the precise mating times for many species of bats are unknown. The aim of this study was to better understand the details and timing of reproductive events in species of bats that die most frequently at wind turbines in North America, because such information can help inform conservation strategies. We examined the reproductive anatomy of hoary bats (Lasiurus cinereus), eastern red bats (L. borealis), and silver-haired bats (Lasionycteris noctivagans) found dead beneath industrial-scale wind turbines to learn more about when they mate. We evaluated 103 L. cinereus, 18 L. borealis, and 47 Ln. noctivagans from wind energy facilities in the United States and Canada. Histological analysis revealed that most male L. cinereus and L. borealis, as well as over half the Ln. noctivagans examined had sperm in the caudae epididymides by late August, indicating readiness to mate. Testes regression in male hoary bats coincided with enlargement of seminal vesicles and apparent growth of keratinized spines on the glans penis. Seasonality of these processes also suggests that mating could occur during August in L. cinereus. Spermatozoa were found in the uterus of an adult female hoary bat collected in September, but not in any other females. Ovaries of all females sampled had growing secondary or tertiary follicles, indicating sexual maturity even in first-year females. Lasiurus cinereus, L. borealis, and Ln. noctivagans are the only North American temperate bats in which most first-year young of both sexes are known to sexually mature in their first autumn. Our findings provide the first detailed information published on the seasonal timing of mating readiness in these species most affected by wind turbines

Total number of keratinized spines on the glans penises of (A) hoary bats (<i>Lasiurus cinereus</i>) and (B) eastern red bats (<i>L. borealis</i>) found dead beneath wind turbines, as a function of Julian day of year (from June 29 [Julian day 180] to October 27 [day 300]).

<p>Total number of keratinized spines on the glans penises of (A) hoary bats (<i>Lasiurus cinereus</i>) and (B) eastern red bats (<i>L. borealis</i>) found dead beneath wind turbines, as a function of Julian day of year (from June 29 [Julian day 180] to October 27 [day 300]).</p

Seminal vesicle length of a subsample of non-necrotic male hoary bats (<i>Lasiurus cinereus</i>) found dead at wind turbines as a function of Julian day of year (from June 29 [Julian day 180] to October 27 [day 300]).

<p>Circles represent adults and triangles represent juveniles. The increasing length of seminal vesicles with time indicates hypertrophy of accessory glands and an increase in libido and secondary sexual function.</p

Testes length of a subsample of non-necrotic male hoary bats (<i>Lasiurus cinereus</i>) found dead at wind turbines as a function of Julian day of year (from June 29 [Julian day 180] to October 27 [day 300]).

<p>Circles represent adults and triangles represent juveniles. The decreasing length of testes with time indicates testicular regression and seasonal termination of primary sexual function (spermatogenesis).</p

The glans penises of adult male hoary bats (<i>Lasiurus cinereus</i>) found dead beneath wind turbines, showing variation in the prevalence and length of well-developed keratinized spines that grow from the surface of the glans and can extend out past its distal tip.

<p>The glans penises of adult male hoary bats (<i>Lasiurus cinereus</i>) found dead beneath wind turbines, showing variation in the prevalence and length of well-developed keratinized spines that grow from the surface of the glans and can extend out past its distal tip.</p

Sperm presence in the caudae epididymides (males) and uteri (females) of hoary bats (<i>Lasiurus cinereus</i>), eastern red bats (<i>L. borealis</i>), and silver-haired bats (<i>Lasionycteris noctivagans</i>) found dead beneath wind turbines, as a function of collection period.

<p>Listed by sex, age (juvenile  =  born in prior 2–3 months), and showing the percentage with sperm during each period and the total across all periods. Numbers in parentheses indicate number of individuals sampled. Sperm presence in the caudae epididymides of males indicates readiness to mate whereas presence in the uteri of females indicates prior successful copulation.</p

Most advanced degree of development of ovarian follicles in individual hoary bats (<i>Lasiurus cinereus</i>), eastern red bats (<i>L. borealis</i>), and silver-haired bats (<i>Lasionycteris noctivagans</i>) found dead beneath wind turbines, by species and age group (juvenile = born in prior 2–3 months).

<p>See text for description of development stages of follicles.</p