SYMBIOSIS 23 



the backs of cattle. In this case the initial puncture was said to be made 

 by the starlings themselves while enucleating the cysts of bot flies and 

 warbles which are located beneath the hide. In any case it is a short 

 step from enlarging an old wound to inflicting a new one. The keas 

 of New Zealand [Nestor notabilis) learned the bad habit of eating flesh 

 off the backs of sheep by the innocent practice of collecting wool for 

 nesting material. The situation is obviously fraught with great danger 

 for both the ox-peckers and starlings and should the balance tip 

 towards parasitism, the starlings' days, at least in the United States, 

 are numbered. 



Apart from this bird there are several common British species which 

 feed fairly regularly if casually among domestic animals. Magpies, 

 jackdaws and rooks are not infrequently seen perched on the backs o 

 sheep, pecking off ecto-parasites and fly-larvae (see tail-piece Chapter 

 1 1) which are often located just beneath the skin. They also work the 

 grazing land for insects and parasitic worms. 



An unusual type of "de-lousing" is carried out by the grey phalarope, 

 a tame, delicate little wader, which is a passage-migrant in Britain. It 

 frequently accompanies surface shoals of large fish and whales, 

 periodically alighting on their backs and removing and eating 

 their ecto-parasites. Aquatic animals are entirely at the mercy 

 of these gruesome creatures, which they acquire in the water 

 and are incapable of dislodging. Pliny noticed with sorrow that 

 "when fishers twitch up their hooks they see a number of these skippers 

 and creepers settled thick about their baits . . . And this vermin is 

 thought to trouble the poor fish in their sleep by night within the sea." 

 Most of us who have witnessed large fish landed in trawls or nets 

 experience a thrill of horror at the sight of the "lice" (Copepoda) and 

 worms plastered on their gills, around their sexual aperture and anus 

 and other tender and vulnerable areas of their bodies. The phalarope's 

 activities must be particularly welcome to whales and one wonders if 

 these animals dehberately rest on the surface with the object of attract- 

 ing their attention. 



Historically the association between the crocodile bird and the 

 crocodile is the most famous symbiotic relationship ever recorded. A 

 translation of the well-known passage by Herodotus is quoted at the 

 head of this chapter. To-day there is no known bird which habitually 

 enters the mouth of the crocodile to de-leech its gums, although 

 Meinertzhagen has seen the Egyptian plover do so on more than one 



