Giant tortoises - cows of the Galapagos

I was invited to accompany the giant tortoise research group to track some of their tortoises in the highlands here on Santa Cruz. We found "Sir David Attenborough", a tortoise named after the inimitable narrator of all life on earth… Anyhow, it's amazing to think that before humans exploited the Galapagos, there were an estimated 300,000 tortoises on the entire island archipeligo. Not often you think of an ectotherm as the predominant grazer in the landscape. Modern day cows (see the background) are common on the inhabited islands as sources of food and milk for people who live here, but on Santa Cruz island, the native tortoise population has rebounded to ~5000 individuals (10 of whom we came across the other day during our hike through the highlands.

Years ago, goats were introduced and became resident and wild and were responsible for outcompeting the tortoises on numerous islands in the Galapagos. The goat eradication program seems to have been a success. So much so that nearly every taxi driver we meet has had a prior job working as a goat eradicator. I presume if it was still lucrative business they would not be driving cabs.