Mammal species that live in urban environments produce more young compared to other mammals. But next to this common ‘winning trait’, mammals deal with different strategies to successfully inhabit cities. This is what Radboud University ecologist Luca Santini and colleagues found in a study that is published on 21 December in Ecology Letters. “This is the first step of many to understand why certain mammals manage to live in cities and why other species don’t.”
Mammals living in urban environments tend to be more of a nuisance to human inhabitants than birds, because they are often regarded as pests — for example rats and bats — and damage structures or goods, as wild boars do. “It’s important to gain more insight into how mammals live in urban environments, so we can eventually achieve a more peaceful coexistence,” Santini says.
Traits that benefit urban mammals
Santini and colleagues collected studies from all over the world that recorded the number of mammal species in cities. “The large number of studies that have already been conducted show that birds in cities, for example crows, tend to be more clever, meaning that they are better able to adapt to unexpected situations. However, mammals in cities are far less investigated, and only studies on a single mammal species, such as bats, have been carried out.
Mammals have way more diverse traits than birds, such as a higher diversity in body structure, size, life-history and ecology. Therefore, we were curious to know whether there are particular traits that are positively affecting the ability of mammal species to flourish in new ecosystems, such as urban environments.”
Larger litters, brains and bodies
The finding that stands out most is that all groups of urban mammals seem to produce more young. Santini explains:
Luca Santini, lead author, Department of Environmental Science, Institute of Water and Wetland Research, Radboud University, Nijmegen, The Netherlands
Differences in other traits were less explicit. “For example a larger brain mass appears to be mostly associated with carnivores and primates who only occasionally visit urban environments, such as jackals, wolves, bears and baboons, rather than with mammals who permanently live in cities, such as genet cats and mongooses among carnivores, or hedgehogs and shrews among insectivores. We also found that carnivores and primates that sporadically visit cities tend to be larger than average. This may be because they need to cover large distances in short times.”
Numbers of mammal species per order found in urban environments. Numbers in parentheses indicate percentage of urban species within the order. The visitors/dwellers category reflects species that due to ambiguous evidence from the literature were included as visitors and as dwellers in the analyses.
Luca Santini et al., 2018. One strategy does not fit all: determinants of urban adaptation in mammals. Ecology Letters.
Open access article under the terms of the Creative Commons Attribution License.
Different strategies for different species
Overall, the results indicate that different groups of mammals use different strategies to deal with the urban environment. “However, because the number of mammal species in an urban environments compared to the total number of mammal species is quite small — 190 out of approximately 6,000 species — this makes the statistics quite challenging, consequently it is hard to make definite statements about specific groups of mammals and traits.”
Santini hopes to investigate further questions in the future, such as which species live in parks, suburbs or city centres and why. “We expect that the number of animals living in urban environments will increase, because urban areas will expand and natural habitat will become more fragmented. Many animals that we believe cannot live in urban areas today, might start visiting and using cities in the future.”
(Source: Radboud University news release, 21.12.2018)
