Interspecific competition between native Eurasian red squirrels and alien grey squirrels: does resource partitioning occur?

  title={Interspecific competition between native Eurasian red squirrels and alien grey squirrels: does resource partitioning occur?},
  author={Lucas Armand Wauters and John Gurnell and Adriano Martinoli and Guido Tosi},
  journal={Behavioral Ecology and Sociobiology},
Abstract. In heterogeneous environments, differential niche selection by two competing species will result in niche partitioning so that individuals of each species can maximise their fitness under different sets of environmental variables. Thus, niche partitioning is considered essential to allow co-existence of ecologically related species. To assess whether niche partitioning was occurring between native red squirrels and alien grey squirrels living together in a 13-ha high-quality mixed… 


Abstract The introduction of alien species can cause competitive exclusion of ecologically similar native species when there is no niche differentiation between them. Such invasive species can

Alien species and interspecific competition: effects of introduced eastern grey squirrels on red squirrel population dynamics

The presence of grey squirrels resulted in a reduction in red squirrel fitness which was evident by lower population summer breeding and a lower recruitment, which will result in a decline in population size and eventually population extinction.

Space invaders: effects of invasive alien Pallas’s squirrel on home range and body mass of native red squirrel

Red squirrels had a reduced body mass and size when in syntopy, confirming that the interspecific competition does not allow red squirrels to reach the optimum body condition that they would have if the competitor was not present.

A grey future for Europe: Sciurus carolinensis is replacing native red squirrels in Italy

Grey squirrel adapt to climate and habitats in both North and South Europe, causing extinction of the native red squirrel, was slow in the first 20 years, but doubled in the successive two decades, and spread was slower than in Ireland and England.

Stress in biological invasions: Introduced invasive grey squirrels increase physiological stress in native Eurasian red squirrels

It is found that the invasive species acts as a stressor which significantly increases the concentrations of glucocorticoids in the native species and reduces body growth and reproductive rate in native red squirrels.

Frontier population dynamics of an invasive squirrel species: Do introduced populations function differently than those in the native range?

Careful comparative demographic study of invading populations could improve management outcomes, indicate differential invasibility of invaded communities, and offer clues to enhance the design of conservation reintroduction projects.

Experimental removals reveal dietary niche partitioning facilitates coexistence between native and introduced species

Diet of MGRS was more closely linked to availability of resources than to presence of Abert's squirrels, and similarity in model species’ diets may make MGRS more vulnerable to competition if climate change eliminates the advantages of larder‐hoarding.


  • C. Romeo
  • Environmental Science, Biology
  • 2014
It is demonstrated that grey squirrels lost part of their parasite fauna during the introduction process and, although they acquired some European parasites, their number does not compensate the number of species lost, with a resulting parasite richness in Italian populations much lower than ingrey squirrels' native range.

The use of species‐specific cone remains of sympatric arboreal rodents to monitor their distribution

It is concluded that determination of consumed cones on cone feeding transects is an accurate and economic method for monitoring presence/absence of red squirrels in those parts of their range where they are sympatric with either edible dormice and/or black rats.

Potential for Nest Site Competition Between Native and Exotic Tree Squirrels

Competition for nests and nest trees appears unlikely given the dissimilarity in use of nest types and tree characteristics, but overlap in microhabitat characteristics increases the likelihood of interspecific competition and could increase the vulnerability of red squirrels to extinction.



Does interspecific competition with introduced grey squirrels affect foraging and food choice of Eurasian red squirrels?

Results provide little support for the food competition hypothesis, but differences in body size between sites suggest that interspecific competition occurs during the growth phase of red squirrels, when juveniles and subadults disperse and look for a place to settle.

Comparative demography of red squirrels ( Sciurus vulgaris ) and grey squirrels ( Sciurus carolinensis ) in deciduous and conifer woodland

Red squirrels had higher survival than grey squirrels in conifers, which may give them an advantage in that habitat, but could also have been explained by a lack of predators on their island study site.

Interspecific competition in tree squirrels: do introduced grey squirrels (Sciurus carolinensis) deplete tree seeds hoarded by red squirrels (S. vulgaris)?

It is suggested that interspecific competition for scatterhoarded seeds, with grey squirrels pilfering red squirrels' food caches, caused a reduced energy intake in red Squirrels with a high degree of interspecific core-area overlap, and reduced body mass in spring.

Ecology and Resource Partitioning among Nine Species of African Rain Forest Squirrels

Nine species of sympatric rain forest tree squirrels were studied in the field and in captivity at Makokou, Gabon and the findings on resource partitioning among them include: two species are restricted to special habitat types and one represents a maximum of taxonomic diversity.

The effects of food availability and winter weather on the dynamics of a grey squirrel population in southern England

It is shown that tree seed availability is the most important factor limiting grey squirrel densities, but this factor both positively and negatively interacts with the severity of winter weather.

Interspecific effects of grey squirrels (Sciurus carolinensis) on the space use and population demography of red squirrels (Sciurus vulgaris) in conifer plantations

The data suggest that adult red squirrels suffered little from interspecific competition with grey squirrels and that the key factor is decreased juvenile recruitment in red Squirrels.

The Mechanism of Replacement of Red Squirrels by Grey Squirrels: A Test of the Interference Competition Hypothesis

It is concluded that interference competition by grey Squirrels cannot explain the large-scale replacement of red by grey squirrels that has occurred in Britain and in Piedmont and that an increase in grey squirrel numbers will augment the intensity of resource competition.

On the replacement of the red squirrel in Britain: a phytotoxic explanation

  • R. KenwardJ. Holm
  • Environmental Science
    Proceedings of the Royal Society of London. Series B: Biological Sciences
  • 1993
Field data from seven separate red and grey squirrel populations, in oak-hazel woods and Scots pines, are used to reject the hypothesis that red squirrel density and breeding is intrinsically poorer than that of grey squirrels.

Squirrels — Medium-Sized Granivores in Woodland Habitats

It will need detailed studies of radio-tagged subadult and adult animals with overlapping home ranges to gain more insight into time-related home range use and behavioural mechanisms that might decrease the intensity of competition for space and food resources in non-territorial tree squirrels.

Effects of temporal and spatial variations in food supply on the space and habitat use of red squirrels (Sciurus vulgaris L.)

The results lend support to the hypothesis of Ostfeld (1985) that when food is sparse and patchily distributed, females should develop intrasexual territoriality, concentrating their activity in food-rich patches, while males should be non-territorial and adapt their space use to the distribution of females.