What would you do if you were one of the last of your species left on the earth? What if you were the only one that could save your species from extinction? Could you handle the pressure of the one task that will determine the fate for the whole of your kind? Not just anyone could do this, but on the remote Chatham Islands to the east of New Zealand one small black robin did just that.
Black Robin (Photo: Frances Schmechel, via wikimedia commons)
Black robins had been numerous on these islands for thousands of years, but with the arrival of humans all this changed. They burnt down parts of the bush to make farmland and brought with them cats and rats. This had a huge negative impact on the black robins and by 1900 they had been wiped out on all but Little Mangere Island. In 1972 a group of wildlife officers could only find 18 black robins left living on the island, and they continued to decline. However it wasn’t until 1976, when only nine robins remained, that a frustrated Don Merton and his team finally got the green light to translocate the remaining robins from the dying bush on Little Mangere Island, to Mangere Island. But when they arrived to the island there were now only seven black robins left, and only two of those were females. And of those two only one was fertile. This female had a blue leg-band, and so subsequently became known as Old Blue. The fate of the entire species now rested on Old Blue’s little shoulders.
Left: Mangere Island; Right Little Mangere Island (Photo: wikimedia commons)
This is where I think the story becomes even more incredible. Black robins normally mate for life, but after the first breeding season on their new island Old Blue and her mate’s eggs proved infertile. Old Blue then abandoned her lifelong mate to partner up with a younger male, Old Yellow (also named after his leg-band). This new unlikely partnership resulted in fertile eggs. From here things gradually started looking up. Black robins only rear one brood of two chicks each year. This means they are unable to recover quickly from such travesties. This is where possibly the biggest accomplishment (of many) of Don Merton’s came into play.
From a childhood memory of him and his brother giving their grandma’s canary a goldfinch chick, which it fostered, Merton developed an ingenious idea to boost the black robin chick numbers. If a black robin’s eggs are taken the pair will lay another clutch. So Don Merton removed the eggs from Old Blue and Old Yellow’s first clutch and placed them instead in a tomtit’s nest. The tomtits fostered the eggs and Old Blue laid two more. When the fostered eggs hatched the chicks were returned to Old Blue and Old Yellow so they would learn the right behaviour of their own species. In this way for each breeding season Don Merton and his team were potentially able to help the black robins raise twice as many chicks than they would have by themselves.
The last incredible thing about this story is that black robins on average live to around 4-6 years. Old Blue however lived to be more than twice this, sadly passing away in 1984 at the ripe old age of 13.
All black robins living today are descendants of Old Blue and Old Yellow. This means at a genetic level all their genes appear to be pretty much identical. This lack of biodiversity within their population makes their species extremely vulnerable to genetic problems. Luckily, so far, there have been no apparent genetic complications. This situation where all members of the species are descended from only a very few select individuals is termed the bottleneck effect.
So, do you think you could handle the pressure to save all of mankind if you were the last fertile being of your gender?
Personally I’m not sure if I could.
I highly recommend this book: Hope for Animals and Their World, by Jane Goodall. It has some very inspiring stories of endangered species from all across the world being rescued from extinction.
Conservation in NZ 