RESEARCH
"Human-altered acoustic environments can be considered a novel selective force impelling change to the communication patterns of many vocalizing species."
- Roca et al. 2016, Shifting song frequencies in response to anthropogenic noise: a meta-analysis on birds and anurans
Passive acoustic monitoring (PAM)
Biodiversity assessments remain one of the most laborious and time-consuming challenges encountered by ecologists and conservation biologists. This task is becoming even more urgent with the the declining frog populations worldwide coupled with current increase of habitat loss. Frogs are one of the most vocally active species and we therefore have the advantage of identifying species diversity by means of their vocalisations. Interpreting acoustic recordings of the natural environment is an increasingly important technique for ecologists wishing to monitor terrestrial ecosystems. Technological advances make it possible to passively accumulate large amounts of data to later be analysed by call recognition software or manually. At the moment we have several monitoring projects that employ this technique. Automated acoustic recorders are deployed in northern KwaZulu Natal, sites include Ndumo Game Reserve (Kwa-Zulu Natal), Tembe Elephant Park, St Lucia, and Sodwana. Amphibian diversity at the Makuleke Contractual Park (the Northern most triangle of the Kruger National Park, also called the Pafuri-triangle) is also monired using PAM.
Read about these projects by clicking HERE!
Amphibian vocal behaviour
Call repertoire variation for the majority of anuran species usually comprise only of slight modifications of the signature advertisement call, e.g. consisting of a single tonal or pulsatile note, a series of identical repeated notes, or a long trill. The extensive variation in the call repertoire of the Common River Frog (Amietia quecketti) has previously been overlooked. This study demonstrates the uniqueness of the call properties of A. quecketti by evaluating the extensive variation in call note types and the occurrence of four nonlinear phenomena.
Click or scan this QR code to
download the poster I presented at
the 2015 International Bioacoustics
Congress in Murnau, Germany.
Urban ecology
Urbanisation is worldwide among the biggest threats to amphibian populations. However, hardly any studies have been conducted on the effects thereof in South Africa. Amphibian distribution and community assemblages are not well understood in aquatic and terrestrial habitats that are rapidly changing due to human modification. High species richness was associated with well-vegetated wetlands, low urban CBD surface area and conductivity, large pond areas and steeper bank slopes. Conductivity and pH showed only weak negative effects on species richness. This is the first study to quantify the effects of urbanization on frog communities in a developing city on the African continent. Our results demonstrate that both local and landscape variables affect amphibians in a small but rapidly developing city. Accordingly, management practices need to adopt a multi-scale approach if we are to conserve amphibians in African cities.
Frog vocalisation in noisy environments
Species communicating acoustically may develop behavioral responses that aid them to transmit information and overcome signal masking in habitats disturbed by anthropogenic noise. Although many studies have concentrated on road traffic noise, very few studies mentioned effects of low flying airplane flyby noise on the vocal behavior of frogs. The Critically Endangered Pickersgill's Reed Frog (Hyperolius pickersgilli) is the focal species in this research where I study the changes in temporal and spectral properties of male vocalisations. Males calling at a higher pitch or calling more intensely during quiet periods may be favoured by being more audible to females and thereby producing male offspring that also call at a higher pitch or with altered behaviour. A large-scale monitoring project is commencing in the 2015 breeding season. Curious? Click HERE!