Rats in Urban Environments
A look at how rats as an invasive species impact urban ecology
Brown rats (Rattus norvegicus)(Armitage, 2004) are an invasive species that are found in every single continent except Antarctica. Native to “northern regions of China, Mongolia, and/or south-eastern Siberia”(Hulme-Beaman, 2021), this species quickly spread through Europe and then to the western hemisphere by the 19th century (Armitage, 2004). Unlike the herbivorous black rats (roof rats), brown rats have a more diverse palette and can survive in a wide variety of conditions, and may even resort to cannibalism in times when food is scarce.
(VictorPest)
In the United States, brown rats are dominantly found inland within big cities that have high population densities. Rats are extremely smart animals and often remember where food has been available. This species has been known to settle in relation to humans and have always maintained a commensal relationship (Hulme-Beaman, 2021).
By following the growth of large groups of humans, rats guarantee the availability of food resources through litter and garbage we leave behind. They also secure shelter and are able to use man-made structures to move unseen. They survive mainly on human scraps as well as anything else that can be eaten without negative consequences(Armitage, 2004). This species shows its resilience through its maintained success in any and all situations.
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Baby Rats (9)
Rats are largely nocturnal and usually become active after sunset into the early morning. Even through reproduction, this species ensures that its numbers won’t be going anywhere. Rats have a very similar method of reproduction to other rodents as they are able to reproduce multiple times a year with litters with upwards of five pups each time. The population in a certain area is extremely resistant to outside forces as one female can have up to 60 young in a year(Armitage, 2004). Rats usually don’t move very far while looking for mates as well; from “Rats About Town: A Systematic Review of Rat Movement in Urban Ecosystems” “When these are readily available [harborage and food in the environment], rats display a strong site fidelity, rarely leaving their home area”(Byers et al, 2019). There are only a few reasons that rats will abandon their nest location. One reason to leave for them is food and shelter. If food availability decreases or nest spots are damaged, relocation is an easy next step in the rat’s journey in life that is aided by urban city structure and the common broken garbage can. In addition to constant reproduction, Brown Rats are very sturdy on an individual level. They are resistant to being hurt and are excellent swimmers. These animals are preyed on by larger mammals and birds(Armitage, 2004), but are mostly killed by humans in urban cities.
Ecologically, brown rats prove beneficial to repelling other species of rats in the areas they populate. The burrows that they live in can also aerate the soil, and they are a good prey population to local predators. Like any other animal too, rats are known as pollinators and aid in seed dispersal due to what they eat and where they inhabit.
Rats found in cities like New York and Chicago tend to cause damage to buildings due to their hard teeth and determination. Burrows in the ground or into homes can damage foundations and pavement(VICTOR). This, along with the diseases associated with ticks and fleas that make their home on these animals, is a high incentive for humans to want them out of the cities.
Brown Rat Distribution
All over urban cities, you will find rat traps and posters warning against leaving food or open trash out. Right next to these things, however, you will usually find an ally with trash and food scraps littered around the garbage cans. Many human attempts at controlling the rat population in larger have been unsuccessful due to the prolific nature of the species. The only way to fully eradicate these animals would be to find some way to completely get rid of open food waste in the entirety of cities. This would take extreme efforts, first to make sure garbage containers are sealed and then to completely stop the opportunity for litter... somehow.
Work Cited
“4 Questions to Ask Before Trying to Catch a Rat”, Victor Pest
Armitage, D. (2004) "Rattus norvegicus", Animal Diversity Web.
“Brown Rat Distribution”, Wikimedia
Byers, Kaylee (2019) ‘Rats About Town: A Systematic Review of Rat Movement in Urban Ecosystems’, Front. Exol. Evol7:13
Hulme-Beaman, Ardern et al. (2021) “The origins of the domesticate brown rat (Rattus norvegicus) and its pathways to domestication.” Animal frontiers : the review magazine of animal agriculture vol. 11,3 78-86.
“Rats in Chicago”, City of Chicago