Plastic ingestion by fishing cats suggests trophic transfer in urban wetlands

Ratnayaka, A. A. W., Serieys, L. E. K., Hangawatte, T. A., Leung, L. K.-P., & Fisher, D. O.(2023). Plastic ingestion by fishing cats suggests trophic transfer in urban wetlands. Environmental Pollution, 316.

Recent studies have suggested that plastic contamination in some terrestrial and freshwater environments is estimated to be greater than that detected in marine environments. Urban wetlands are prone to plastic pollution but levels of contamination in their wildlife are poorly quantified. We collected 276 fishing cat (Prionailurus viverrinus) scat samples in Colombo, Sri Lanka for a dietary study of urban fishing cats. We used traditional dietary analysis methodology to investigate the contents of the scats by washing, isolating, and identifying prey remains; while sorting prey remains of individual scats, we unexpectedly detected macroscopic (>1 mm) plastic debris in six (2.17%) of the samples. Across all scat samples, we detected low occurrences of microplastics (0.72%), mesoplastics (1.09%) and macroplastics (1.45%). All three plastic types were found in scats containing rodent remains, while meso-, and macroplastics were found in scats with avian remains, and micro- and macroplastics in scats containing freshwater fish remains. Given that felids are obligate generalist carnivores that eat live or recently dead prey and do not consume garbage, our findings suggest that trophic transfer of plastics occurred whereby fishing cats consumed prey contaminated with plastic. Although macroscopic plastic detection was low, our findings suggest that accumulation of plastics is occurring in wetland food webs, and plastic pollution in freshwater terrestrial systems could pose a risk to predators that do not directly consume plastics but inhabit contaminated environments.

Urban habitat use and home ranges of fishing cats in Colombo, Sri Lanka

Ratnayaka, A. A. W., Serieys, L. E. K., Prasad, T., Leighton, G. R. M., Sanderson, J. G., & Leung, L. K.-P. (2021). Urban habitat use and home ranges of fishing cats in Colombo, Sri Lanka. Mammalian Biology, 102, 217-277.

Urbanisation and habitat loss are major threats to wildlife populations globally. Understanding how species respond to anthropogenic changes is therefore crucial to mitigating threats and developing conservation management strategies. We examined the habitat use of five fishing cats (Prionailurus viverrinus) in Sri Lanka’s capital city, Colombo, a densely urbanised landscape with a mosaic of wetland habitats, cultivated areas, and altered open spaces. We investigated: (1) to what extent all five cats used human-impacted versus natural wetland habitat; (2) whether there were behavioural shifts to avoid human activity throughout the diel cycle; (3) the home range sizes of two resident females and one resident male, and the extent of the area used by the two translocated males; (4) whether the two translocated males would survive introduction to a new urban environment. We monitored the fishing cats for 637 days (mean = 127) and collected a total of 2278 GPS (5-h interval) collar locations. We found that all five individuals used highly urbanised areas more than we expected. Home range sizes of the three residents were smaller than fishing cat home ranges in less disturbed landscapes. Though our sample size was small, our findings suggest that fishing cats use urbanised areas in Colombo, particularly at night, likely to avoid daytime human activity. Further comprehensive ecological study is needed to explore the aspects of fishing cat ecology that facilitate their persistence, and aid in their conservation across increasingly urbanised areas.

Map of the study sites and habitat types. Study sites are enclosed within their respective coloured squares.

First pictures of fishing cats in hyper urban landscape Colombo Sri Lanka

Ratnayaka, A. A. W. (2021). First pictures of fishing cats in hyper urban landscape Colombo Sri Lanka. CATnews, 73, 19-20.

The fishing cat Prionailurus viverrinus is a small wild cat that is often associated with water-rich habitats such as wetlands and mangroves. In Colombo, Sri Lanka, the presence of fishing cats in the city’s urban wetlands was confirmed in 2004, but no data was available after that. In this follow-up study, my team and I confirmed the presence of fishing cats within the city proper in 2015 and again in 2017, making this the first photographic record of fishing cats in a hyper urban landscape.

Security camera footage of a fishing cat (UFC2m) fishing for Japanese koi at an outdoor fishpond in Colombo 05 in 2015 (Photo Eshan Witane).