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2008 ). However, hybridization has yet to be fully studied in Laos, or in many
of the regions where it occurs. Recently, artificial disturbance of macaques
has occurred in many SE Asian countries, including translocation of popu-
lations and release of pet macaques, and sometimes this movement causes
human-induced inter-mixing of species (Hamada et al ., 2006a ). For example,
in Vietnam, where long-tailed macaques were distributed in the area of 16˚N
or lower (Dang et al ., 2008 ), their range has widened to latitudes higher than
18˚N (Nhan, 2004 ), perhaps due to transfer by humans, and rhesus macaques
were also artificially transferred to lower latitudes (Cat Tien National Park,
around 11.5˚N; Polet et al ., 2004 ), which may be expanding their region of
overlap and thus increasing the potential for hybridization to occur.
Tail length is one indicator of hybridization. The Indochinese long-tailed
macaque population, distributed to the north of the Isthmus of Kra (ca. 10.5˚N),
tends to have shorter tails (100-120 percent or crown-rump length; Hamada
et al ., 2008 ) than its counterpart distributed to the south (120-130 percent;
Hamada et al ., 2008 ), which suggests the introgression from rhesus macaques.
Rhesus macaques in the eastern half of the Indochina Peninsula, on the other
hand, have longer tails (50-80 percent; Hamada et al ., in preparation) than
their conspecifics to the north (China and vicinity, 35 percent, Hamada et al .,
2005 ) and west (India and vicinity, 45 percent, Hamada et al ., 2005 ), which
indicates the Indochinese rhesus population has received introgression from
long-tailed macaques. Aside from morphological evidence, hybridization of the
two species has also been suggested from molecular analyses (Tosi et al ., 2002 ;
Denduangboripant et al ., 2005; Malaivijitnond et al ., 2008 ). Rhesus macaque
populations in Laos are of importance to delineate the history and mechanism of
hybridization because of their natural overlap with long-tailed macaques here.
Based on field surveys, we report here the distribution, tail-length vari-
ation, and present status of the rhesus and long-tailed macaques in southern
Laos. Taking the distribution patterns of macaques in Thailand (Malaivijitnond
et al ., 2005 ) and Vietnam (Hamada et al ., 2010) into consideration, we provide
implications for macaque phylogeography, including impact of hybridization
on long-tailed and rhesus macaques in Laos. We also estimate the national
population of long-tailed macaques and discuss the conservation issues and the
status of long-tailed macaques in Laos.
Methods
We carried out field surveys to cover southern Laos ( Figure 3.1 ) and inter-
viewed people along several routes. From 8-13 July 2005, 18-26 January 2007,
and 6-14 September 2008, we surveyed from Bolikhamxay to the southern
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