From poison to plastic: how rodents introduce harmful substances into food webs
- twedewer
- Apr 28, 2024
- 4 min read
Cooke, Raylene, et al. “Widespread Exposure of Powerful Owls to Second-Generation Anticoagulant Rodenticides in Australia Spans an Urban to Agricultural and Forest Landscape.” The Science of the Total Environment, vol. 819, 2022, pp. 153024–153024, https://doi.org/10.1016/j.scitotenv.2022.153024.
Where and how did you find this article?
I found this article through the University of California-Santa Cruz’s library database.
Briefly summarize the research study being reported --what were the methods?
Australian researchers collected 18 tissue samples from dead powerful owls. Collection sites were divided along a gradient of urbanization, ranging from entirely natural to entirely urban. They analyzed the prevalence of 8 common rodenticides, 4 toxic heavy metals (mercury, lead, cadmium, arsenic), and a broad screen of 187 agricultural chemicals.
rodenticides detected in 83.3% (almost 4 in every 5) of the owls
What conclusions do the scientists make based on their findings?
“Proximity to urban development can facilitate owl exposure to toxicants (Lohr, 2018). We examined powerful owls from different land use types but the prevalence of brodifacoum did not vary with position along the urban to agricultural/forest gradient, in which most birds sampled had detectable levels of SGARs, regardless of the degree of urbanization. This indicates that powerful owls inhabiting all areas, not just those residing in highly urban or agricultural areas, are exposed to rodenticides. Given that SGARs (mostly brodifacoum) can be purchased for domestic, commercial, industrial and agricultural use in and around buildings from many hardware stores or supermarkets, the secondary effects on food webs cannot be ignored.”
Ecosystem heavy metal levels aren’t high enough to indicate alarming prevalence in Australian ecosystems used in the study, but the presence of heavy metals in birds of prey reduces their quality of life.
Brodifacoum (a second-generation anticoagulant rodenticide) is present at sometimes lethal levels in powerful owls, despite their diet consisting of opossums, who are exposed less to SGARs than target rodent populations (owls native to Australia whose diet is predominantly rodents have been found to have higher concentrations of SGARs in dead tissue).
“Powerful owls do not scavenge but prey upon arboreal marsupials, and generally not rodents, suggesting that brodifacoum is entering the powerful owl food web via accidental or deliberate poisoning of non-target species (possums)”
Further research is required into understanding how possums contact rodenticides.
“Presence of brodifacoum was detected across the complete urban-forest/agriculture gradient, suggesting widespread exposure.”
How does this study help us better understand something about the animal?
Owls (and likely all birds of prey) can ingest significant amounts of harmful rodenticide through animals that aren’t directly targeted by SGARs.
Although concentrations of harmful chemicals/heavy metals aren’t always lethal, they degenerate quality of life for birds of prey by affecting “fitness, reproduction, and immune function” (Rattner et al., 2014).
All owls are exposed to rodenticides.
Do you think you can tell a story about this study, and if so, who would you make the protagonist, and why? (you're not committing to anything here)
I can write a brief story about this study, although the protagonist (powerful owls) is dead in the study, therefore I would expand upon how living powerful owls are affected by the study’s findings. A story about this study would do better to focus on rodenticide’s harmful ecosystem effects, how humans worsen these effects, how humans can reduce rodenticidal ecosystem harm, and how rodenticide poses the most danger to predators high in the food chain.
Nessi, Alessandro, et al. “Microplastic Contamination in Terrestrial Ecosystems: A Study Using Barn Owl (Tyto Alba) Pellets.” Chemosphere (Oxford), vol. 308, 2022, pp. 136281–136281, https://doi.org/10.1016/j.chemosphere.2022.136281.
Where and how did you find this article?
I found this article through the University of California-Santa Cruz’s library database.
Briefly summarize the research study being reported --what were the methods?
Researchers analyzed barn owl pellets for microplastics (MPs). Barn owls are chosen because they’re generalists, strongly associated with agricultural environments (therefore effective MP indicators), they don’t stray far from their homes (easy, consistent sample collection), and they mainly consume small rodents/insectivores (who directly consume MPs). Samples were analyzed for microplastics and determined that MPs were present in 33% of owl pellets (one third!).
What conclusions do the scientists make based on their findings?
Highest microplastic occurrence in barn owls was found in areas where barn owls prey on synanthropic (ecologically associated with humans) rodents, specifically brown rats. This “may indicate habitat degradation and increased exposure to MPs.”
“Our results confirm the occurrence of MPs in the environment and suggest the transfer of these contaminants through the food chain.”
“Most detected fibres consisted of PET and PAN, polymers typically used for clothing and home textiles. This is an indication that in our study area, a major source of MP might be atmospheric deposition since the largest portion of MP in the atmosphere consists of fibres (Henry et al., 2019), and synthetic clothing has been reported as the largest source of airborne MP (mostly polyester; Dris et al., 2016).”
Herbivorous rodents are less exposed to microplastic digestion.
Routine owl pellet analysis can determine lifelong trends in owl diet, especially MP trends.
How does this study help us better understand something about the animal?
This study furthers our understanding of how microplastics enter the food chain through prey/primary consumers and accumulate as they move up the chain through/towards predators. It identifies the barn owl and its generalist diet as an effective measure of microplastic contamination in agricultural landscapes, allowing more accurate assessment of contamination pathways,
Do you think you can tell a story about this study, and if so, who would you make the protagonist, and why? (you're not committing to anything here)
I absolutely could tell a story about this study, although it would be drab. Since researchers measured information from owl pellets, there were no live specimens, therefore the protagonist would be microplastics in terrestrial ecosystems. Not very interesting from the get go.
Hey there! I totally feel you on this microplastic issue. It's crazy how much we're seeing about plastic pollution these days, especially on Twitter. It's like every time I scroll through my feed, there's another article or study talking about how it's affecting wildlife and ecosystems. That owl pellet study you mentioned is really interesting. It's clear we need to do something about this problem before it gets even more out of hand. Thanks for sharing your thoughts on this!