Libro de Resúmenes / Book of Abstracts (Español/English)

Resumenes 160
Obtaining population parameters for Rhea americana
from individual characteristics.
The aim of this work is obtain the parameters for the Shape-Lotka´s
equation, to be used for modeling the population dynamics of ñandú. The
model is defined by:
⎧ L(
a ) B(
t − a ) 0 ≤ a ≤ t
ρ(
a,
t ) = ⎨
⎩π(
a − t,
a ) ϕ(
a − t ) t < a
∞
( t ) = β(
a ) ρ(
a,
t ) da (B.C)
B ∫
0
where B(t) is the number of births at time t, β (a) is the maternity function,
ρ(a,t) is the number of individuals between age a and a+da at time t, L(a)
is the probability of an individual living to age a, π(α,a) is the probability the
individual will be alive at age a if it is alive at age α and ϕ(a-t) is the
number of individuals alive at age a at time t [5] .
The parameters to calculate are two, the fertility (β) and the survival
(L) since π(α,a) and B(t) are deduced from them.
For estimating the fertility, an energy balance was done since it is
possible to determine from it if an individual has the energy needed to be
able to reproduce. Hence the number of offspring can be estimated.
For an individual to reproduce it is necessary that during the non
breeding season sufficient energy had been stored to face the costs of
reproduction. So it is necessary to know the amount and the characteristics
of food ingested by each individual to determine the metabolizable energy
that is provided. The daily costs can be estimated through two different
forms: one by means of allometric equations that involve the weight of the
individual [1, 2, 4] , whereas the other is obtained through the time that the
individual allocates to each activity and the energetic cost of every one of
them [6, 7, 8] .
Both the amount of food that an individual ingests and the daily
activity costs are related to the weight of the individual. Therefore it is
important to know the relationship between age and weight. With such aim
the weight of rheas from birth until reaching the maximum size are being
monitored. This monitoring requires differentiating females from males
because size is sex dependent. Once the daily assimilated energy and total
daily energy costs for an individual are known, it is possible determine if he
will be able to reproduce.
The survival function will be estimated from the curve obtained from
monitoring of offspring born and reared in extensive farms.
Referencias
[1] Grawford E.C. y R.C. Lasiewski. (1968). Oxygen Consumption and
Respiratory Evaporation of the Emu and Rhea. The Condor 70: 333-339.
[2] Jensen J. y J. Harvey Johnson. (1992). Husbandry and Medical Managment
of Ostriches, Emus and Rheas. Chapter 4: Nutrition.College Station, Tx., pp.
129.
[3] Kooijman S. A. L. M. (2000). Dynamic Energy and Mass Budgets in Biological
Systems. 2 ed. Cambridge University Press.