PATTERNS OF LOSS ACROSS ISLAND TAXA 313bird ever recorded, the giant elephantbird
(Aepyornis maximus). Other losses include 2 giant
tortoises, pygmy hippo, and at least 14 species of
lemur, most of them larger than any surviving
species (Diamond 1991b; Groombridge 1992).
The islands of Amsterdam and St Paul, some
2500 km east of Madagascar in the southern Indian
Ocean, and 80 km from each other, are known to
have had their own avifauna, but nearly all of the
native species were exterminated through fires and
the introduction of domesticated and commensal
mammals, notably feral cattle (Olson and Jouventin
1996). The extinct avifauna included a species of
rail, and a different species of duck on each island.
The ducks can be assumed to have been different
species because remains of the Amsterdam form,
Anas marecula, reveal it to have been small and
flightless: whatever was on the other island (known
only from an historical account) must perforce have
been a distinct form.
Without doubt the most celebrated of all extinct
island birds, the dodo (Raphus cucullatus) was a
large, flightless pigeon (Columbiformes) endemic
to Mauritius (Livezey 1993). A related species, the
solitaire (Pezophaps solitaria), occurred on
Rodrigues, also in the Mascarene group. The exis-
tence of a third species on Réunion is indicated by
historical evidence, but has not been backed up by
a specimen. The dodo and its relatives were wiped
out by the early eighteenth century by a combina-
tion of hunting, habitat destruction, and the nega-
tive impacts of introduced vertebrates. Predators
implicated include pigs, rats, cats (especially on
Rodrigues), and monkeys (Mauritius only).
Introduced herbivores responsible for significant
destruction of native vegetation were cattle, goats,
and deer (Mauritius only). Although they proved to
be vulnerable to the evolutionarily unpredictable
intervention of humankind, these giant, ground-
dwelling pigeons were formerly dominant con-
sumers within their respective island ecosystems.
The native forests and woodlands of Mauritius
have been reduced in extent by 95% to just 5% of
the land area (Safford 1997). This deforestation,
combined with the introductions of many exotic
animals and plants, has led to the extinction of at
least eight other endemic bird species in addition to
the dodo and the reduction to critical levels of eight
others. Five of the six extant forest-living native
passerines are essentially restricted to native vege-
tation. Moreover, only a small fraction of this habi-
tat is of good quality because of nest predation,
reduced food supply, disease, and, in the past, the
use of organochlorine pesticides. In 1993, each of
these five species was estimated to have popula-
tions of the order of only 100–300 pairs. Safford
(1997) recommends management of exotic
browsers and predators, and weed removal, as part
of a broader strategy for conservation on Mauritius.
He also suggests that, given the impracticality of
eliminating predators on the mainland, some of the
offshore islets be considered for ecological rehabili-
tation and translocation programmes. However, he
notes that bird populations on small offshore islets
would be vulnerable to catastrophes, especially
cyclones.Reptiles
Caseet al. (1992) review the data for reptilian
extinctions worldwide over the past 10 000 years,
noting that the great majority have occurred on
islands (as Table 11.2) and as a consequence of
human impacts. On small islands, humans have
raised extinction rates by about an order of magni-
tude, but rates of loss have been much lower on
very large islands. Introduced predators, princi-
pally mongooses, rats, cats, and dogs, have been
the main agents of human-related extinctions,
whereas competition with introduced reptiles
appears to have had relatively little impact on
native island reptiles. The reptiles most prone to
extinction have been those with relatively large
body size and endemics with a long history of
island isolation.
Caseet al. (1992) subdivide islands into three cat-
egories:
●First, they discuss islands colonized in prehistory
by aboriginal people and then colonized later by
Europeans. On such islands, many reptiles are
known only as subfossils, having become extinct
during the aboriginal period. In New Zealand, for
example, three species of lizard known from the