Published: May 31, 2017It's green, leafy and important to zoos - it's browse...
Browse - what is it, and why is it important? Browse as a noun means the leaves, shoots and twigs of shrubs and trees used as food for animals like cattle and deer. And for many zoo animals, too.
Domestic cattle are browsers as well as grazers. You can see the evidence anywhere cows are in with low-growing trees – they create a browse line, a horizontal line at the base of the canopy that marks the level to which they can reach. Zoo herbivores are kept more or less like cattle on well-run farms; they have grass, bagged food and silage material – and any browse they can reach or are given.
Pretty much any plant left unprotected is knocked over, rubbed up against, chewed, dug up and of course eaten by browsers. To stop them driving the gardeners to distraction and to give them as much fresh, ‘natural’, food as we can, we grow browse. Yes, zoos nurture trees and shrubs to produce the leafy, twiggy branches the browsers love.
As well as being good for the animals, there are many other reasons why producing our own browse makes perfect sense: it comes with almost zero food miles, no chemicals are used, it doesn’t depend on intensive agriculture and our land can be managed sympathetically for nature as well as browse.
The gardens team is responsible for planting, growing and harvesting ever-increasing quantities of browse in the Zoo grounds. They work closely with keepers to produce as much as possible, and to do it in a genuinely sustainable and ecologically rich landscape.
We cultivate different browse plants for different reasons: some species are fast growing, so produce material quickly; variety is good, because animals don’t always want the same old stuff all the time; and we grow evergreen varieties to ensure a year-round supply. Some animal species will eat the bark or tree itself when no leaves are present, or even when they are.
As with all food sources, there are plants that need to be avoided due to toxicity: oak and acorns have been associated with gastrointestinal tract problems in sheep, goats and horses; oleander and yew can kill mammal species; and plants that are not poisonous can still cause stomach obstructions if they are not digestible.
Species such as evergreen oak can only be fed in smaller quantities or infrequently to allow the animals a chance to naturally dispose of the large amount of tannins they produce. This is also the reason that some animals will refuse to eat certain plants altogether – they’re not always being fussy!
Not surprisingly, the giraffe herd and Duchess the African elephant consume the most browse, though taken together the primates get through a fair amount, too. Different plants provide different nutrients – animals need a balanced diet, just like us. Also, browse is often the closest foodstuff we can provide to a “wild diet”, so it can have some important health implications, too.
Browse, then, is important to animals and therefore important to the people who care for them. These simple, leafy branches keep large parts of so many zoos running smoothly. So, the next time you walk under a tree or prune a garden shrub, think of what it might mean to a zoo animal.