Table 3.

Parameters from models predicting change in mean tusk circumference at lip in African elephants between 1966–1968 (historical elephant populations) and 2005–2013 (contemporary elephant populations). Tusk measurements are in centimeters

Regression covariates	Coefficient	Standard error	T statistic	Probability
Contemporary elephants born in 1995 onwards compared with 1966–1968 elephants of similar age
Males
Intercept	20.062	0.185	108.209	<0.0001
Shoulder height	4.491	0.162	27.771	<0.0001
2005–2013 relative to 1966–1968	−1.120	0.376	−2.977	0.0033
Females
Intercept	15.248	0.138	110.200	<0.0001
Shoulder height	2.466	0.139	17.760	<0.0001
Contemporary elephants born by 1970 (Survivors) compared with 1966–1968 elephants of similar age
Males
Intercept	44.708	1.049	42.634	<0.0001
2005–2013 relative to 1966–1968	−3.565	1.253	−2.845	0.0108
Females
Intercept	24.755	0.374	66.112	<0.0001
Shoulder height	1.148	0.416	2.761	0.0089
2005–2013 relative to 1966–1968	−2.703	0.909	−2.973	0.0052
Shoulder height × 2005–2013	−1.559	0.748	−2.085	0.0440