Bat aggregational response to pest caterpillar emergence

Area of Science:

• Ecology
• Zoology
• Entomology

Background:

• Moths (Lepidoptera) are significant agricultural and forest pests globally, causing substantial economic damage.
• Two specific inchworm species, Operophtera brumata and Erannis defoliaria, are noted for extensive foliage consumption as caterpillars.
• Bats are hypothesized to potentially regulate pest caterpillar populations by preying on them.

Purpose of the Study:

• To investigate the role of insectivorous bats in controlling pest caterpillar populations.
• To determine if bat foraging behavior changes in response to caterpillar outbreaks.
• To identify specific bat species that prey on Operophtera brumata and Erannis defoliaria.

Main Methods:

• Field studies were conducted at two infested and one control forest sites.
• Caterpillar infestation levels were quantified through sampling during spring.
• Bat flight activity and foraging behavior were monitored using acoustic monitoring and direct observation.
• Bat fecal samples were collected and analyzed for DNA of target caterpillar species.

Main Results:

• Bat fecal samples revealed significant consumption of Operophtera brumata (51.85%) and Erannis defoliaria (29.63%).
• Foraging activity of gleaning bats (Myotis nattereri, Myotis bechsteinii) increased at caterpillar-infested sites.
• Foraging activity of Plecotus auritus/austriacus, utilizing both gleaning and aerial hawking, also increased at infested sites.
• Bat activity did not increase at the control site, indicating a response to prey availability.

Conclusions:

• Bats, including both specialist and generalist gleaners, aggregate at sites with high pest caterpillar abundance.
• These bats exhibit dietary flexibility, switching foraging strategies to exploit abundant prey like caterpillars.
• The findings confirm the significant potential of bats as a natural biological control agent for reducing pest caterpillar populations.