Common noctules – one of the largest bat species native to Germany – are searching for their fellows during their hunt for insects above farmland. Scientists from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) show in a paper published in the journal “Oikos” that bats forage on their own in insect-rich forests, but hunt collectively in groups over insect-poor farmland. They seem to zoom in on places where conspecifics emit echolocations during the capture of insects, an inadvertent clue that reveals high-yielding areas to others. However, “listening” to their hunting companions to find food only works when sufficient numbers of bats forage in the same area. If numbers continue to decline, density could fall below a critical level and joint hunting could become difficult or impossible. This could pose an additional threat to the survival of species such as the Common noctule.

Similar to humans, wild animals’ reaction to disturbance is accompanied by releasing hormones, such as cortisol. To understand the impact of various “stress” factors – for example competition for food, encounters with predators, or changing environmental conditions – on wildlife, scientists first need to determine the baseline levels of relevant hormones for each species. Researchers from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) now uncovered possible pitfalls of the commonly used hormone analysis method that overestimate concentrations of cortisol and thus lead to overstated conclusions. They investigated whether glucocortiocoid hormones deposited in animal hair can be reliable biomarkers to indicate the impact of disturbances. The source of errors in the commonly used antibody-based enzyme immunoassays (EIA) method is described in a recently published article in the scientific journal “Conservation Physiology”.