Wildlife conservation experts at the University of Brighton and Nottingham Trent University analysed hundreds of videos supplied by members of the public to investigate interactions within and between different species.
The researchers found that while food left by people in urban gardens – leftovers or commercially bought for this purpose – can provide benefits for wild animals, it can also bring competitors and predators into close proximity.
While badgers tended to dominate other species in the garden hierarchy, hedgehogs were also found to have more clashes than expected, the study revealed.
Aggressive and submissive behaviour among animals in the footage was found to be more common than neutral interactions – from 316 instances where animals were spotted together 175 ended in confrontation.
Animals were more likely to confront different species than their own. Cats and foxes were found to take a particular disliking to one another, with more than three-quarters of interactions (77%) sparking some form of aggressive or defensive reaction – with cats dominating foxes.
Badgers out-competed all species in the contest for food – and to the research team’s surprise hedgehogs out-competed cats. They suggest this may be due the fact that domestic cats are not as physically or behaviourally well adapted to defend themselves against hedgehog spines as wild predators.
Within the same species, hedgehogs were found to be the most combative – with more than half (55%) of interactions between hedgehogs leading to some form of aggression.
This included a characteristic behaviour termed ‘barge and roll’ by the researchers, whereby one hedgehog attacks another by running at it, causing the victim to roll up before being pushed away by the assailant.
The researchers suggest the purpose appeared to be to move a rival away from the food, such as to the edge of the garden. In one case, an individual was pushed down a flight of concrete, and another into water.
Within species, badgers were the least competitive with one another, with just seven percent of encounters resulting in a stand-off.
The researchers say that with regards to hedgehogs specifically – a declining species – understanding their behaviour and interactions is critical for informing conservation and welfare management, including feeding practices.
“Food provided by people may help wild animals but may also attract animals together that could compete, injure, or predate each other,” said Professor Dawn Scott, lead researcher from Nottingham Trent University’s School of Animal, Rural and Environmental Sciences.
She said: “The consequences of interactions between garden mammals are numerous and can become aggressive between competing species. It could lead to injury or death and increased competition might also reduce access to resources for subordinate species or individuals.
“Our study is the first to quantify interactions between urban mammal communities in this way and to identify hierarchical relationships between wild and domestic mammals in urban gardens.
“We need to better understand interactions between urban animals and the potential effects of providing food in this way, to ensure any potential risks are minimised.”
Dr Bryony Tolhurst at the University of Brighton said: “Feeding wildlife in gardens can also potentially unwittingly increase disease transmission between wild animals, and between wildlife and pets, by gathering them together.
“We need to understand the balance of costs and benefits of feeding animals in urban gardens, to properly guide people on how best to improve their welfare and conservation.”
The study Garden Scraps: Agonistic Interactions between Hedgehogs and Sympatric Mammals in Urban Gardens is published in the journal Animals, and also involved researchers from the University of Sussex and the Spanish National Research Council (CSIC).