Figure 1.
Overview of research aims, where (1) Sample collection involved head and foot (pes) measurements from (a.) a captive population of pouch-young pademelons [25] and (b.) a cross-sectional cull of a single cohort of pademelons [20] followed by (2) model selection for describing the life history growth of pademelons; followed by the development of (3) a smoothly joining two-phase (SJ2P) model; for (4) the improved accuracy of characterising and describing the lifetime growth of animals with disparate growth phases in order to enable an improved understanding of the age structure, survival and demographic behaviour of individuals and populations.
Figure 2.
The growth of juvenile Tasmanian pademelons (Thylogale billardierii) during the pouch phase of their life-history.
Black circles represent (A) pes length and (B) head length of pouch young (mm); blue squares represent the Verhulst logistic model used to describe (A) pes length and (B) head length growth (mm) during pouch life(Length = A+K.L0/((K−L0).e(−r . Age)+L0, r2 = 0.98). Post-weaned pes length growth is represented for(C) males and (D) females, where black circles represent pes length (mm) of pouch young and aqua squares represent the Brody model used to describe post-weaned pes length growth(Eqn.5). Pes Length = A C; L = B. (1−C.e−k . Age), r2 = 0.71, and r2 = 0.44 respectively for males and females.
Table 1.
Coefficients of the Logistic and von Bertalanffy growth models describing pes length growth of pouch young and post-weaned Tasmanian pademelons (Thylogale billardierii).
Figure 3.
The life-time growth of (A) male and (B) female Tasmanian pademelons (Thylogale billardierii) (black circles) and the Brody growth function (black line) fitted on the entire pes length data (pes length = a+b * (1−exp(−k * Age)).
Figure 4.
The sequence of steps showing the construction of growth functions for the growth phases of (a) male and (b) female Tasmanian pademelons (Thylogale billardierii).
Panels a1 and b1 show previously recorded data [25] (black circles) and predicted pes lengths using the Verhulst logistic model (blue filled circles) for pouch young. Panels a2 and b2 show pes lengths of post-weaned animals (black circles) and predicted pes lengths using the Brody growth function (aqua circles) (join point j = 207 days). Panels a3 and b3 show animal age (months) using pes length as the predictor variable, for the observed life of pademelons (black circles) and the converged SJ2P model (black line).
Figure 5.
The SJ2P model describes the lifetime growth (pes length) of the Tasmanian pademelon (Thylogale billardierii).
Red circles denote female pes length and red dashed line shows the SJ2P model describing growth of females from birth to 80 months of age; blue circles denote male pes length and blue line shows the growth of males from birth to 80 months.
Table 2.
Coefficients of the linear and Brody growth models describing head length growth of pouch young and post-weaned Tasmanian pademelons (Thylogale billardierii).