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Head to the link in our  description to get 10% off. “As might be expected in an oceanic island, the  mammals are both few in number and of small size. The collections brought back by the  officers of H.

M. S. "Flying Fish” and by Mr. Lister included two species of  rat…, a large fruit-bat…, and a shrew…; a small insectivorous bat was seen,  but no specimens were obtained.

The conditions of life are apparently extremely  favourable, food being always abundant... The consequence of this is that all the  species of mammals are extremely common,   and the individuals are always exceedingly fat.” [♪♪ INTRO ♪♪] Christmas Island is an island of endlings. Islands, especially ones with  long histories of isolation,   tend to be hot spots for species that are  found nowhere else on Earth, which also makes   them uniquely vulnerable to extinction when that  isolation ends.

Christmas Island is no exception. Of its five native mammals mentioned in the intro,   only one is left, the large  fruit bat or flying fox. The other four have gone extinct  along with several reptile species.

And the weird thing is the birds of Christmas  Island are the cause, or at least their poop is. Though perhaps it is unfair to blame the  birds for the fate of the other wildlife   on Christmas Island when really it's a story  about how we humans decide what we value. The products of animals or the animals themselves. [♪♪ MUSIC ♪♪] Many stories about Christmas  Island start with its naming   by Captain William Mynors after he  sighted it on Christmas Day, 1643.

It’s a very human way to frame its history – like it just appeared out of the  Indian Ocean in the early 1600s,   when it first began showing up on the  maps of English and Dutch navigators. But, of course, its history goes  back much further, to when it… actually first appeared out of the ocean. Christmas Island is a seamount, a mountain that rises from the seafloor, and, in this case, that  mountain was also a volcano.

It stretches 5000 m up from the floor of the ocean  and likely surfaced around 60 million years ago,   making up the core of the island and allowing  for the formation of a ring of reefs. It began to sink back beneath the  waves about 40 million years later,   becoming covered in coral, which eventually  turned into thick deposits of limestone. Then, around five million years ago, it rose up  again thanks to some flexing of tectonic plates,   which pushed that limestone above the  surface of the ocean and transformed   it into an island around which  a new coral atoll could grow.

And sometime after that,  animals got there…somehow. Now, Christmas Island is about 1500  kilometers from Western Australia and   less than 500 kilometers from Jakarta, Indonesia. It’s perhaps less mysterious  how bats made their way there,   but that’s a pretty long way  to go for a lizard or a rat,   and the Island had several endemic species of both  that were not found anywhere else on the planet.

They probably got there by floating  on mats of vegetation or uprooted   trees carried by the Indonesian Throughflow,   a major ocean current that runs from the  western Pacific into the eastern Indian Ocean. And, of course, birds have found the Island a  number of times since it reemerged from the ocean. There are something like six endemic species  that make their home on Christmas Island,   and many more that breed there.

And with 80,000 birds nesting  annually comes a lot of poop… which is where things started to go wrong for  the land-locked inhabitants of the Island. See, when bird guano is rained  on or pounded by ocean surf,   nitrogen and phosphate compounds  are washed out of the poop. If this happens on a surface like limestone,  which is high in calcium carbonate, chemical reactions turn this combination into hardened phosphate deposits, which are highly  sought-after for producing fertilizer.

And all the ecological turmoil on Christmas Island   is rooted in the discovery of these  deposits of phosphate in the 1880s – a discovery that turned a small island in  the Indian Ocean into something valuable: a resource to be exploited. Christmas Island was annexed by Britain in 1888,   then leased to the owners of the Christmas  Island Phosphate Company for 99 years. Mining began in 1899, with the first  major shipment going out in 1900.

And it continued until March of 1942, when  Japanese soldiers invaded the island during World War II,  seeking control over its  phosphate and its strategic location. After the war, mining resumed, but the  next decades brought about some changes – like Christmas Island became an  Australian territory in 1958… And environmental concerns in  the 1970s about endemic seabird   nesting sites spurred the creation of  Christmas Island National Park in 1980. More of the island and its surrounding waters  were added to the protected area over the next nine years,  perhaps marking a turning point  in what resources were considered valuable.

Meanwhile, in 1987, dwindling quantities  of high-quality phosphate and low prices   led the Australian government to close the mines. The phosphate itself, it  seemed, had lost its value… at least for the moment. The mines were re-opened in 1990, with  the current lease set to run out in 2034.

And while the human history of Christmas Island  has largely been a story of the value of its   geological resources, its biological ones have  been slipping through our fingers the entire time. In early September of 1900 – the same year the first major shipment  of phosphate left the Island – the SS Hindoustan arrived, off-loading  cargo and taking on 3300 tons of phosphate. Part of that cargo included bales of  hay and with them came black rats.

Now, Christmas Island already  had two species of native rat: Maclear’s rat and the bulldog rat. Maclear’s rat was described as  being arboreal and nocturnal,   and extremely common,  occurring in literal ‘swarms.’ The bulldog rat was also nocturnal, but  lived on the ground and dug burrows. It was less common than Maclear’s  rat, but was said to have a thick   layer of fat on its back, suggesting that  the two rats weren’t competing for food.

By October of 1904, though, neither  native rat could be found on the Island – only black rats were left. It seems that they had carried  with them a cargo of their own: fleas infected with a parasite to  which the native rats had no immunity. We will likely never know the endlings  of Maclear’s rat and the bulldog rat,   but what remains of these two species are  nine museum specimens whose value now lies   in their ability to shed light  on the cause of their extinction.

And, just four years later, in 1908,   a third native mammal was also  thought to be gone for good: the Christmas Island shrew. Like Maclear’s rat, it had been extremely  common when it was first described… and the loss of the two rats may  have been behind its rapid decline – but not its extinction. Because the shrew actually wasn’t extinct  by 1908; it had just become very rare.

It wasn’t seen again until 1958,   when two individuals were caught during the  clearance of more rainforest for mining. They were released and decades  passed before any more turned up. This time, it was December of 1984, with  biologists capturing a single, lone female… and not realizing her value at the time.

A possible mate for her was found in March  of 1985, but he died soon after being caught. The death of the female, the probable endling, sometime in 1985 or 1986, marked  the final sighting of this species. It’s possible that they, like the native rats,   were also decimated by the parasite  carried by the fleas of the black rat.

But another hypothesis suggests  it was actually the loss of the   native rats that caused their  decline, by allowing another   iconic Christmas Island species to take  over: the Christmas Island red crab. If these crabs were preyed upon by the  rats, then without that balancing force,   their population could increase.  And these crabs consume leaf litter,   which was both a habitat for the shrews  and sheltered their arthropod prey. Without enough leaf litter, the shrews would be  pushed into habitats they were less suited-to,   dwindling in number until the  accidental introduction of the   common wolf snake in the 1980s finished them off.

Either way, the Christmas  Island shrew was officially   declared extinct in October of 2025  after decades of fruitless surveys. And it was not the only native mammal  to be declared extinct in the 2000s. The endling of the smaller of the two bats,   the Christmas Island pipistrelle,  was last heard on August 26th, 2009, and the species was officially  listed as extinct in 2016.

Like the rats and the shrew, it was  abundant and widespread when mining began,   and it seemed to be doing well up until  about 1994, when its numbers began to drop. But, unlike its fellow mammals,  we can’t point to a single cause, it seems to have been a perfect storm of invasive  wolf snakes, giant centipedes, and yellow crazy ants, plus a cyclone in 1988 destroying  roosts and ongoing habitat loss from mining. Now, only the larger bat, the  Christmas Island flying fox, remains.

It’s a kind of endling, itself, the last surviving endemic mammal on the island. And it, too, is threatened  by the phosphate mines, or, at least, their dust. The phosphate deposits on the Island  are naturally enriched with the heavy   metal cadmium and mining them  creates potentially toxic dust.

Elevated levels of cadmium have been found on  the fur of flying foxes and in their urine. While it’s not clear yet whether this  has contributed to the decline in their   population since the 1980s, it is a  concern, along with the constellation   of invasive species and extreme weather  events that took out the pipistrelle. And it’s an ongoing one,   as phosphates are still being extracted  from the Island, at least until 2034.

As long as this continues,   there will continue to be a tension in  the perceived value of Christmas Island. Environmental concerns about  the mines began in the 1970s,   yet half of the endemic mammal extinctions  happened after the creation of the national park. It seeks to brand itself as the  Galápagos of the Indian Ocean,   attracting ecotourists, and  yet, the mines are still open.

It remains to be seen what  will happen after they close. Will the flying fox population  have stopped declining    or will we have met their endling by then? And if none are left, will ecotourists instead only get to witness the thing that made Christmas  Island valuable in the first place: its birds? [♪♪ MUSIC ♪♪] The many tragic stories of species we’ve driven  to extinction that we’ve covered so far on Endlings might have left you wondering  how we humans manage to sleep at night.

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