Urban canyon effect: storm drains enhance call characteristics of the Mientien tree frog

Abstract

Anthropogenic structures, such as wall surfaces, may change the acoustic environment for signals transmitted by animals, creating novel environments that animals must either adapt to or abandon. Animals can potentially use those structures to manipulate sound characteristics. In many anuran species, successful reproduction depends on long-range propagation and perception of advertisement calls. Callers may select natural perches or human-made objects to assist call propagation. Male Mientien tree frogs Kurixalus idiootocus frequently perch and call in roadside concrete drainages -miniature urban canyons. We used a combination of field and indoor experiments to test two hypotheses: (1) transmission of calls emitted inside drains is enhanced; (2) males selected perches inside drains that facilitated call transmission. A field survey indicated that male Mientien tree frogs preferred calling inside rather than outside drains. A playback showed that calls emitted from inside drains were enhanced in both amplitude and note duration. In an indoor experiment using a replica of a concrete drain, males preferred one particular type of call perch. However, we found no difference in sound properties between random locations inside the drain model and the perch location preferred by calling males.Storm drains enhance calls of a tree frog W.-H. Tan et al.

Adaptive changes in sexual signalling in response to urbanization

“…Increased signal conspicuousness through more complex calls thus provides a selective benefit to urban males in terms of mate attraction, without incurring the cost of increased predation or parasitism. Previous studies of urban-associated conditions have argued that changes in sexual signalling can either be adaptive or maladaptive 23,58 . Our results provide evidence that urban males can display an adaptive phenotype that may have resulted either as a direct response to changes in the environment or as an indirect response to changes in the sexual and natural selection pressures that operate on the phenotype.…”

Rethinking creative intelligence: comparative psychology and the concept of creativity

“…As a starting point for evidence of improvisation in animals, we might look at the many cases of startlingly novel behaviours adopted by species in response to novel environmental contingencies. To give one recent example, Mientian tree frogs in Taiwan have taken to using storm drains to enhance the volume and duration of their mating calls (Tan et al 2014), seemingly showing an ability to adapt behaviour to novel environmental contingencies. Other famous cases include the discovery that great tits in the UK had learned to peck through the lids of milk bottles to drink the cream inside (Hinde and Fisher 1951) and the emergence of the novel behaviour among Japanese macaques of washing off soil and debris from sweet potatoes (Kawai 1965).…”

Chimpanzees use tree species with a resonant timbre for accumulative stone throwing

“…Additionally, some species use flexible behaviours to optimize acoustic signals relative to their environment. For example, frogs will select tree holes [2] and drainage pipes [3] that better resonate their calls. Similarly, tree crickets use leaves as acoustic baffles to increase the intensity of their sounds [4].…”