Understanding stable bi-female grouping in gibbons: feeding competition and reproductive success

Table 6 Inter-birth intervals of wild gibbon populations

Species	Inter-birth interval (month)	Range (month)	N	Grouping pattern	Literature
Hylobates lar	41 ± 9.1	34-71	17	Pair, Bi-male	[42]
	120		1	Pair	[43]
	26.5	22-31	2	Pair	[44]
H. agilis	38.4 ± 4.8		5	Pair	[45]
Hoolock leuconedys	49		1	Pair	Fan PF, unpublished data
Symphalangus syndactylus	33.7 ± 3.5	28.5-38.1	5	Pair, Bi-male	[46]
	60	48-72	2	Pair	[43]
	>36		3	Pair	[44]
Nomascus hainanus ¹	24 ± 1.6	22-26	4	Bi-female	[20]
N. concolor	42.3 ± 9.2	37-53	3	Bi-female	[23]
N. nasutus	31 ± 6.6	23-38	8	Bi-female	Present study

¹Calculated from Table II in [20]. Only birth dates of consecutive infants known to within a month were used to calculate the inter-birth interval.

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