m.r.Life ι**=7/3ψ

Bird and mammal life histories

Bird & Mammal Populations contain a complete life history model for all bird and mammal species with a body mass estimate. The life history of a species is often seen as a multi-dimensional trait of the individual, but from an evolutionary point of view it is more informatively viewed as a multi-dimensional trait of the population. This is because it is the feed-back selection of the population that selects and regulates the life history to an equilibrium with no population dynamic growth.

This natural selection of a balanced life history by the underlying flow of energy in populations of interacting individuals is the focus of Malthusian relativity. The selection is used by Bird & Mammal Populations (BMP) to estimate 14,353 life history models based on the principles in Witting (2017a,b). Each of the life history models in BMP reconciles the physiology of individuals with the interactive foraging ecology at the evolutionarily determined population dynamic equilibrium.

Fig. 1 Distributions of the phylogenetic levels of the inter-specific estimators for the different life history parameters. Estimator level: data (dark grey), genus (blue), family (green), order (yellow), and class (red). Elaborated from Witting (2021).

Estimation and uncertainty

The estimation of the life history models in BMP follows Witting (2021). This implies the incorporation of life history parameters from multiple databases available in the literature, including among others body mass estimates from Smith et al. (2004) and Dunning (2007); metabolic rates from McKechnie and Wolf (2004), McNab (2008), and Hudson et al. (2013); parameters on reproduction, physiological time periods, and individual growth from Jetz et al. (2008), De Magalhaes and Costa (2009), Jones et al. (2009), and Myhrvold et al. (2015); and ecological traits like population density and home range from Damuth (1987), Tucker et al. (2014), Tamburello et al. (2015), Nasrinpour et al. (2017), and Santini et al. (2018).

These data provide more than 55,000 individual estimates of parameters across all species of birds and mammals, with BMP estimating the remaining missing parameters by allometric inter-specific extrapolation. The result is a complete life history model for each species, which includes estimates of metabolism, net assimilated energy, individual growth, mortality, fecundity, age of reproductive maturity, generation time, life span, home range, population density, biomass, population consumption, and a relative measure of intra-specific interactive competition (with a selection of traits listed for each species in BMP).

Table. 1 The precision of an estimated missing value for a parameter is given by a coefficient of variation (cv) that is estimated from missing value predictions of n known data points. Estimator level: genus (blue), family (green), order (yellow), and class (red). Elaborated from Witting (2021).

The underlying data have not been collected as a random sample across the different species and they are thus phylogenetically unevenly distributed. This means that the uncertainties of the missing value estimates increase with the phylogenetic distance to the nearest species with data. To capture this uneven distribution of uncertainties, BMP uses a missing parameter estimator that differentiates between the different phylogenetic levels, with the distributions of estimator levels shown in Fig. 1. This provides separate estimates of uncertainty for the different parameters at the different phylogenetic estimator levels (Table 1). The uncertainty is visualised for each life history by a colour code, where data are presented in black and missing parameter estimates at the genus, family, order, and class levels are presented in blue, green, yellow, and red.

Click here to read how a few axes of selection explain life history variation in birds and mammals.


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