The interplay between seasonality and density: consequences for female breeding decisions in a small cyclic herbivore

Table 3 Best model parameters

ZERO PART of the best model (explaining breeding probability)
Explanatory variable	Estimate	Std. Error	z value	p-value
(Intercept)	-6.0575	0.4876	-12.4242	0.0000
PCA1	0.0568	0.0594	0.9567	0.3387
PCA2	-0.2772	0.0972	-2.8509	0.0044
BL	0.0495	0.0041	11.9786	0.0000
BC	0.7641	0.4746	1.6100	0.1074
NDVI	0.0123	0.0032	3.7885	0.0002
Temp	-0.0017	0.0291	-0.0595	0.9526
Ab	-0.042	0.0132	-3.1861	0.0014
PCA2 : BC	0.9505	0.3198	2.9722	0.003
PCA2 : NDVI	-0.0074	0.0027	-2.738	0.0062
PCA2 : Temp	0.0505	0.0232	2.1708	0.0299
PCA2 : Ab	-0.0202	0.0078	-2.5672	0.0103
PCA1 : BC	0.5083	0.1905	2.6685	0.0076
PCA1 : Ab	-0.0094	0.0045	-2.0955	0.0361
PCA1 : PCA2	-0.0904	0.0480	-1.8814	0.0599
COUNT PART of the best model (explaining litter size)
Explanatory variable	Estimate	Std. Error	z value	p-value
(Intercept)	0.578	0.2407	2.4013	0.0163
PCA2	-0.3396	0.1659	-2.0466	0.0407
BL	0.0082	0.0019	4.3701	0.0000
NDVI	0.0022	0.0010	2.2656	0.0235
PastAb	-0.0086	0.0043	-2.022	0.0432
PCA2 : BL	0.002	0.0013	1.5126	0.1304

Best model parameters explaining common vole female per capita productivity (number of embryos per females) in Western France. Model used was mixture model (“hurdle”) with two parts: a zero part explaining the breeding probability with binomial distribution and logit link (zero versus superior to zero); the second part explaining the litter size (distribution of values superior to zero occulting all zero counts) with a Poisson distribution and a log link (variable definition; PastAb: past June abundance, PCA1: first axe of PCA, BC: body condition, Ab: current density, Temp: anomalies of temperatures, PCA2: second axe of PCA, NDVI : anomalies of NDVI, BL: body length).

ISSN: 1472-6785