 I study the effects of kangaroos on the environment which includes reptiles, birds, invertebrates. What I found is when you have more kangaroos you have less grass. There are very different numbers of reptiles in the different levels of grass. So when you have a very heavily grazed lawn-like structure I didn't get many reptiles and I didn't get many species of reptiles. As the grass got taller I started getting a lot more reptiles and a lot more species of reptile. This is a striped legless lizard, Delma Impa. It lives in grasslands and it relies on grass tusks for shelter and food. It may look a little bit like a snake, but it is a lizard. It's just lost its legs through time. That's an adaptation to living in grasslands. Like many species on this planet, this guy is threatened from habitat loss. He relies on natural grasslands to survive and over 95% of natural grasslands in Australia have been modified or cleared for agriculture. So where we do have grasslands left, like we do here, it's really important to protect them. And if we don't control kangaroo grazing, this guy is literally eaten out of house and home. Kangaroos are native, but the system has changed. We don't have indigenous hunting anymore and the main native predator of kangaroos, the dingo, has been eradicated. And so in these dramatically altered systems kangaroo numbers can skyrocket and that means a lot less grass for the other critters to live in these habitats. Many ACT reserves have kangaroo densities of over 200 kangaroos per square kilometre. And what we found is that reptiles like this guy require kangaroo grazing of about 100 kangaroos per square kilometre. We can't just look up reserves and throw away the key. If we want to conserve species, we have to actively manage these reserves.