Understanding the low breeding success in Greater Rheas populations through an energy budget model

SIMOY, M. VERÓNICA; CANZIANI, GRACIELAA; FERNANDEZ, GUSTAVO J.; MARINELLI, CLAUDIA B,

ECOLOGICAL COMPLEXITY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 vol. 18 p. 10 - 24

1476-945X

We propose an individual-based energy budget model of the Greater Rhea (Rhea americana) with thepurpose of analyzing the population?s recruitment. One remarkable characteristic of this species is thatfemale rheas lay eggs communally and males incubate the eggs and care for the chicks without theassistance of females.The model is based on a system of equations daily updating the weight of each bird as a function of itsingestion rate and the energetic cost of its activity pattern. Ingestion rate is calculated from fieldexperiments. Daily energetic costs are estimated from activity patterns observed in the field, taking intoaccount gender and factors that influence behavior (e.g., photoperiod, season). Concatenating dailymodel outputs, the weight dynamics of an individual can be calculated over any given period of time.The possible factors that affect the successful breeding of the Greater Rhea and therefore populationgrowth are analyzed using the model. Different reproductive strategies for each gender are analyzed andthe minimal body weight, and thus energy reserves, that an individual needs to achieve for ensuringreproductive success is determined. Model outputs show that the reproductive success of males dependsstrongly on their body weight while females exhibit low nutritional requirements for producing eggs. Ananalysis of model outputs allows inferring that males in wild populations might not be able to breed inconsecutive years but could successfully breed every other year. They also allow estimating theincidence that food availability has on population growth. Management strategies that are easy toimplement in extensive and semi-extensive farms may allow obtaining male individuals capable ofbreeding every year.