Wednesday, February 24, 2010

A tale of three species

I was on the upper part of the Rock of Gibraltar today. Barbary Macaques were up to their usual pranks along the crest of the Rock irritating nesting Yellow-legged Gulls

A Peregrine came over to create an unlikely picture of three species each with its own story to tell and brought together by accidents of history. Like so much in ecology, history has had a major role to play in shaping distribution patterns.

Let's start with the Peregrine. A number of pairs breed on the Rock and they have done so for millennia. The Victorian naturalists, notably Howard Irby and Willoughby Verner, saw them on the Rock but they were already recent observations. The Peregrines have been here at least 50 thousand years! The pictures below, from my archive, show fossil Peregrine material that we have excavated from 50-40 thousand year old levels in Gorham's Cave. So the Neanderthals were familiar with the local Peregrines, but were they with the other two players in today's game?

Peregrine tarsometatarsus from Gorham's Cave

Peregrine sacrum from Gorham's Cave

They certainly were not familiar with the sight of Barbary Macaques on the Rock. Despite twenty years of excavation we have never found fossil macaques in our caves. These macaques were certainly in Europe in the Pliocene and for much of the Pleistocene, where they reached north into the United Kingdom, Germany and Austria, but they disappeared mostly by the last-but-one interglacial, Marine Isotope Stage 7, around 200-odd thousand years ago. The ones on the Rock were brought in by the British military as part of the importation of "game from Barbary" in the 18th Century, and they went feral.

They weren't always as numerous as they are today but their habits of coming into people's houses seem to go back some way. Many visitors have described the macaques, among them George Orwell when he visited the Rock in September 1938:

The Barbary Ape is said to be now very rare at Gibraltar & the authorities are trying to exterminate them as they are a nuisance. At a certain season of the year (owing to shortage of food I suppose) they come down from the rock & invade peoples' houses & gardens. They are described as large doglike ape with only a short stump of tail. The same species found on the African coast just opposite.

And what of the gulls? Well, we certainly have gull fossil material from the days of the Peregrine but they may be Herring Gulls. I suspect the Yellow-legged Gull expansion is a recent phenomenon. Irby and Verner certainly don't describe a colony on the Rock in the thousands and I think that the increase, from my own recollection, happened in the late 1970s shortly before the Audouin's Gull boom.

So three species with different stories to tell, came together one spring day of 2010! I wonder what they make of it all?

Trickle of migrants today: Black Kite, Short-toed Eagle, Swallow (lots), House Martin, Hoopoe, Goldfinch, Linnet, Chiffchaff...

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