Hi everyone! For this week, let me share with you a “crime scene” I witnessed on 10 August 2020.
“Malaysian Pied Fantail” by Tony Castro
The victim is a Sunda Pied Fantail (Rhipidura javanica). It was unfortunately killed by this free-ranging domestic cat (FRDC).
As a veterinary nurse, I instinctively wanted to save the bird, but it was visible that the muscles have stiffened via rigor mortis – meaning it has died for some time. The cat did not seem to be interested in consuming the bird and left. I analysed the bird’s body but did not find any blood or bite wounds, from this I recall a myth that birds can be frightened to death from getting chased by predators…? Out of curiosity, I did a quick research to find out if anyone debunked that myth.
While I couldn’t find concrete articles if getting chased by predators can frighten birds to death. I did find out that fear of predators’ sounds has caused song sparrows (Melospiza melodia) to alter nesting behaviour which reduced offspring numbers by 40% in a controlled study. Even though song sparrows are “least concerned” under IUCN, a change in the population numbers in one trophic level can potentially disrupt a whole ecosystem.
I’ll get back to the bigger picture – Cat predation.
Pie-chart of predation numbers in the United States, statistics by Loss et al. (2013)
In a study by Loss et al. (2013), predation numbers were derived using probability distribution parameters based on different studies here Additionally, the FRDCs have caused extinctions of 63 species worldwide (Doherty et al., 2016). All the unique adaptation processes developed through evolution, all gone.
I can’t imagine how many ecosystems have been disrupted and the ecological processes that are lost – such as seed dispersal and pollination by the birds (Trouwborst et al., 2020). The reduced seed dispersal rates inevitably lower the abundance of producers (usually plants) that form the base of the food chains of all ecosystems. The plants photosynthesise using sunlight to produce glucose, allowing energy to flow from one trophic level to another. Not to forget the medicinal values the native plants may carry and how they regulate our atmosphere via oxygen production.
It’s no wonder Feline catus is listed as one of the top 100 invasive species in the world by IUCN.
Previously, I did not cover how stray dogs are “invasive alien species” as well. Why are stray dogs and cats termed as aliens, the extra-terrestrial beings? The domesticated dog and cat species have no native range of their own, meaning they do not occur naturally in the wild. This is especially since humans have controlled their breeding process and even their distribution. In the case humans intentionally or unintentionally introduce the domesticated species into the natural wild spaces, they become “aliens”. Needless to say, they are invasive due to their threats to wildlife and native biodiversity.
To end off, owned FRDCs with outdoor access contributes to about 744,000 of the annual bird mortality rate. I believe that these 744k deaths can easily be prevented if only the owners have kept them in their homes securely, a simple move, to minimise threats to biodiversity.
Since humans introduced these domesticated species into the natural spaces, it’s time we do more to help.
Paws out!
References:
Doherty, T. S., Glen, A. S., Nimmo, D. G., Ritchie, E. G., & Dickman, C. R. (2016). Invasive predators and global biodiversity loss. Proceedings of the National Academy of Sciences of the United States of America, 113, 11261–11265. https://doi.org/10.1073/pnas.1602480113
Loss, S., Will, T. & Marra, P. The impact of free-ranging domestic cats on wildlife of the United States. Nat Commun 4, 1396 (2013). https://doi.org/10.1038/ncomms2380
Trouwborst, A, McCormack, PC, Martínez Camacho, E. Domestic cats and their impacts on biodiversity: A blind spot in the application of nature conservation law. People Nat. 2020; 2: 235– 250. https://doi.org/10.1002/pan3.10073