Armadillo Invasion

The species has a high reproductive rate, producing quadruplets and living for twenty years. Individuals can also delay implantation of a fertilised egg during times of stress.

Image: By (Own work) [CC-BY-3.0 (], via Wikimedia Commons

By Flora Haynes
BSc Ecology and Conservation @FloraHaynes

Migrations of species northwards, to areas previously thought unsuitable,  are becoming more common. Red foxes are encroaching on Arctic fox territories, and grizzly bears on polar bear territories. In the United States the nine-banded armadillo (Dasypus novemcinctus) is among the documented species joining this great migration. The range expansion has been remarkably quick; nearly ten times the expected rate for a mammal, and is thought to be due in part to climate change.

The species’ history sheds some light on its rapid expansion. D. novemcinctus was not found in the States before 1850, because there were barriers to its dispersal. These included the Rio Grande, which is a wide river. Although armadillos can swim there was no suitable habitat once individuals had crossed the river. They like scrub or woodland which provide cover. At the time, fire management meant the area consisted predominately of prairie grasses. Hunting from humans, and predation by wolves and panthers also prevented a viable population establishing itself. However, after settlers had inhabited Texas the barriers were reduced, including the physical barrier posed by the Rio Grande. Increased river travel by humans meant increased translocation of D. novemcinctus, which was still a food source. The increased population density on the Texan side led to range expansion. This was aided by humans, both accidentally and intentionally, including stowaways on cattle trains and zoo and circus escapees.

So why is D. novemcinctus able to colonise areas so quickly? The species has a high reproductive rate, producing quadruplets and living for twenty years. Individuals can also delay implantation of a fertilised egg during times of stress.

However, their expansion is limited by temperature and precipitation constraints; they need a constant water source and cannot survive in areas where the mean January temperature is below -2°C. Despite these limitations, it is predicted they could live in New York and even Canada if appropriate translocation occurs.

Milder winters in the states are enabling southern species to invade northern ecosystems bringing worries that native species will be displaced and ecosystems disrupted. Although the rapid expansion of D. novemcinctus is unusual, further climate change is imminent and invasions from the South are likely to increase, each bringing its own ecological and economical impacts.

Find out more:


Armadillo Fact File

Armadillo moving across North America


One Comment

  • Really interesting blog, told me something I didn’t know!

    Anna Taylor 27th October 2011 at 11:48 am Reply
Leave a Comment

Your email address will not be published.*

Tick the box or answer the captcha.

You might also like

  • Autumnal Wonders And Where To See Them

    Autumn is a season like no other; one of colour, action and perpetual movement. A season which I cherish above all others, which marks the start of a number of subliminal wild spectacles, as many species begin preparations for the winter

    By James Common
  • The Forest Gardeners of Madagascar

    A large proportion of trees in Madagascar’s rainforest have fruits that are eaten by lemurs and for some species, lemurs are the primary or only animal that can distribute their seeds

    By Alex Taylor
  • Deadly Fungus Spreads

    Although habitat loss is still the largest threat to amphibians worldwide, habitat protection is now no guarantee of survival, because the spread of a deadly fungus is reaching even the most secluded habitats.

    By Alex Taylor
  • If young people hope for a greener future, they must act now.

    For every one person that takes a stand for a brighter future, however, it is safe to assume that there are ten that do not. People who do not, necessarily, care any less about the environment than their more vocal counterparts. But fail to act nevertheless. It is these people, in our day of ceaseless ecological ignorance, that we need more than ever.

    By James Common