Elephants Elephants - Wildpro - Twycross Zoo

animals in Sri Lanka as well as direct observations (Fernando and Lande
2000). Four groups were observed in detail ranging in size from seven to 19
animals. There was a lower level of association between group members
compared with African savannah animals and solitary ranging females were
observed. The genetic analysis showed that all individuals within a social
group shared the same mtDNA haplotype and that all these must have
descended from a single female in the recent past. Groups with overlapping
ranges maintained their maternal genetic identity, suggesting that females do
not transfer between groups. However two groups which shared a haplotype
had a greater overlap in their home ranges, but did not associate with each
other. Smaller group sizes were found in the rain forest of Malaya and
Sumatra (Eltringham 1982). Santiapillai and Supahman (1995) found group
sizes of 4-8 animals in the forests of Way Kambas in Sumatra but larger
aggregations of up to 45 animals were found in areas of grassland; however
smaller groups were more common in the dry season. They compare this to
group sizes observed by Oliver in Malaysia averaging five or six animals.
Less is known of the social organisation of African forest elephants but group
size is much smaller, averaging 2.4 individuals. There, groups seem to consist
of single mother family units (Turkalo and Fay 1995), with older males being
solitary.
It appears therefore, from evidence to date, that elephants living in forest and
woodland habitats may tend to split into smaller units more frequently than
those in savannah and have less direct inter-group contact.
Male calves leave the family unit on reaching sexual maturity and join up with
other males and may form bull herds which are very unstable in composition.
Younger bulls may hang around the family units but older bulls spend little
time with them and tend to be solitary. The home range of a cow herd is
much larger than the area used by a given male, hence cow herds will pass
through the home ranges of several different males. Data from Sri Lanka
suggest that the nursing units may have smaller home ranges (Kurt 1974)
(McKay 1973).
SEXUAL BEHAVIOUR
Female Asian elephants show a cycle length of 14-16 weeks and African
females of 14 weeks (Oerke et al 2000). This is a relatively long oestrus cycle
with a brief 1 week receptive period (Rasmussen and Schulte 1998). A
considerable amount of research has taken place to obtain detailed
information on the elephant ovarian cycle since early work in the 1980’s
(Plotka et al 1988) and this is reviewed (Hodges J.K. 1998). Female elephants
advertise forthcoming ovulation to males by characteristic behaviour patterns
which include: oestrus walk (head held high, eyes wide open and tail may be
raised), chase, mounting and consort behaviour (Moss 1983); these patterns
are shown for 2-6 days. Asian females also advertise a forthcoming ovulation
by releasing (Z)-7-dodecenyl acetate in urine during the pre-ovulatory phase
to signal to males of their readiness to mate (Rasmussen and Schulte 1998)
(Rasmussen 2001), however this compound has not been found in African
females (Riddle and Rasmussen 2001). Females also produce a unique
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