Science Behind the Photo #27

running cows, cattle, pantanal, wetland

James Pope

Eight million cows roam Brazil’s Pantanal – the world’s largest wetland – and with all that beef chomping through the area’s vegetation, environmentalists are nervous that native mammals could be pushed out.  However, a recent dung study shows their fears may be unfounded.

The Pantanal has been home to cattle ranchers since the mid-18th century.  Today, 95% of the area is privately owned by farmers who feed the fast food outlets of Brazil’s burgeoning cities.

As well as bringing much-needed income, the cows provide a fire-fighting service in the dry season by clearing large amounts of highly-flammable plant debris.  But despite the benefits, there’s serious concern that competition for food could cause problems for indigenous pampas deer and capybara – a sort of giant guinea pig.

To understand the issue better, scientists from Brazil and Scotland collected dung from the three mammals and analysed what they’d been eating.

Their results, published in Mammalian Biology, show that deer have completely different taste to cows – preferring leaves and shrubs.  And, while capybara go for the same grasses as cattle, the scientists saw that grazing cows keep the overall grass length down, allowing succulent new shoots to grow which are far more nutritious for the outsize rodents.

So it seems cattle ranching, if kept at current intensities, might actually be good for local wildlife.  “It is one of the very few examples of sustainable management in a tropical biome,” say the scientists.

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