Sex-ratio theory in conservation biology

Tella, José Luis

doi:10.1016/s0169-5347(00)02075-9

Cited by 31 publications

(30 citation statements)

References 12 publications

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“…Considering that breeding from highly inbred individuals is not necessarily bad because they might still be genetically important at population level, in practice, the manager of this captive population might be able to combine inbred females with unrelated or slightly unrelated partners, resulting in a non-or slightly inbred offspring (very likely a daughter if our results are considered), which help to solve the short term practical problem of surplus males within the EEP of the species. This practice suggested for captive Cuvier's gazelle agrees with that outlined by other authors: in captive breeding populations where offspring sex ratio is dependent on female condition, manipulation of offspring sex ratios should be considered as a management option as it may increase the number of females that can be released (Lenz et al, 2007, Robertson et al, 2006, Tella, 2001). …”

Section: Implication To Ex Situ Conservation Programssupporting

confidence: 85%

Mother traits and offspring sex in two threatened gazelle species in captivity

Moreno

Ibáñez

Barbosa

2011

Journal for Nature Conservation

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Since threatened species are generally incapable of surviving in their natural environments, ex situ conservation programs are required to preserve them from total extinction. Captive breeding provides the tool to rear sustained populations. Knowledge about biology of such species is critical for managing such breeding programmes. In this paper we look at the sex variation in calves surviving to 30 days in captive populations of two endangered polygynous gazelles, Gazella cuvieri and Gazella dama mhorr. We examined which of the following mother traits may affect sex allocation: her age, experience and inbreeding coefficient. Because twins are quite common in Cuvier's gazelle, we also analyze whether offspring sex is mediated by litter size in this gazelle.In both species the overall sex ratio did not differ from unity at the age of 30 days.These results support the suggestion that for a given population to be in equilibrium, a 1:1 calf sex ratio is to be expected, with females in good condition producing sons and females in poor condition producing daughters. We also found that offspring sex is not significantly related to the same mother traits in the two gazelles studied. Cuvier's gazelle findings showed that only maternal inbreeding influenced offspring sex, the less inbred the mother the higher the probability of producing sons. In contrast, none of the maternal traits studied were related to offspring sex in Mohor gazelle. Two non exclusive explanations are given to justify differences observed between these two species; one relate to a probable differential cost of producing either sex; the other refers to the actual homozygosis level in captive populations of each species. For Cuvier's gazelle litter size has no effect on offspring sex when the sex of the littermate is taken into account. This result fit predictions derived from Trivers-Willard model: mother in good conditions (less inbred) produce the sex with higher fitness returns (i.e., male), no matter if born at single or twins brood. Many variables are likely to affect progeny sex ratio. We have presently examined only a few. But our results might be of interest in management decisions and conservation programs such as reintroductions.

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Section: Implication To Ex Situ Conservation Programssupporting

confidence: 85%

Mother traits and offspring sex in two threatened gazelle species in captivity

Moreno

Ibáñez

Barbosa

2011

Journal for Nature Conservation

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“…Sex-ratio theory predicts that in species with large variance in male reproductive success, females in better condition may maximise their fitness by producing more male offspring (Trivers and Willard 1973). Tella (2001) suggested that provision of supplementary food could lead to the male-biased offspring sex ratios seen in many zoos. The overall 1:1 sex ratio found in this study is in line with other lynx studies both from captive (47.6% males, Kaczensky 1991) and wild populations (48.7% males, Breitenmoser-Wu¨rsten et al…”

Section: Discussionmentioning

confidence: 99%

“…Ovary analyses of free-ranging lynx have shown 50% fertility in 10-month-old females and 100% fertility in 22-monthold females, but indicated that primiparous females breed later in the mating season than multiparous females (Kvam 1990). Furthermore, studies of captive felids have documented that there is a strong male-biased sex ratio in litters born to ad libitum fed animals (Tella 2001). Thus, here we will describe variation in timing of birth and birth sex ratio.…”

Section: Introductionmentioning

confidence: 95%

Reproductive biology of captive female Eurasian lynx, Lynx lynx

et al. 2005

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Studies on wild Eurasian lynx (Lynx lynx) have revealed variation in reproduction between areas, years and individuals. In order to explore potential causes for this variation other than food supply, we analysed data from captive lynx, which provide conditions with minimal environmental variation as all were fed ad libitum. Data from 37 individual female lynx were available from 20 zoos in Norway, Sweden, Finland, Switzerland and the Czech Republic. Data on 177 reproductive events (where a male was available to the female at mating time) are presented. Of these events, 85% resulted in litters being born. Average litter size was 1.95, with a variation from 1 to 4. The mean birth date was 26th May, and sex ratio was not significantly different from parity. The probability of reproduction was related to age, with fewer litters produced by the very young (2-3-year old), and no sign of a senescence effect. However, a clear effect of senescence on litter size was evident. The captive lynx did not have higher reproductive rates than wild lynx, indicating that either factors other than food supply are driving the variation in wild lynx reproduction, or that a factor such as stress may be causing additional variation in the captive population.

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“…The kakapo may be an example here. Supplementary feeding of the few remaining individuals of that species may have led to malebiased sex ratios because females in good conditions turned out to be more likely to have sons than daughters (Tella 2001, Clout et al 2002. At one point in time, about 70% of all recorded offspring of this species were sons.…”

Section: Manipulating the Rearing Environment Or Maternal Decisionsmentioning

confidence: 94%

“…Moreover, in species where population growth is limited by the availability of oocytes, male-biased sex ratios directly reduce population growth. For example, the remaining population of the critically endangered kakapo (Strigops habroptilus) of New Zealand has been found to be significantly male biased, probably as an undesirable side effect of supplementary feeding (Tella 2001, Clout et al 2002. Because this parrot is also a species for which population growth is severely limited by egg production, manipulating family sex ratios towards more daughters (by methods that are outlined below) quickly became one of the priorities of the conservation management of this species (Robertson et al 2006).…”

Section: Why?mentioning

confidence: 99%

Managing Population Sex Ratios in Conservation Practice: How and Why?

Wedekind¹

2012

Topics in Conservation Biology

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Sex-ratio theory in conservation biology

Cited by 31 publications

References 12 publications

Mother traits and offspring sex in two threatened gazelle species in captivity

Mother traits and offspring sex in two threatened gazelle species in captivity

Reproductive biology of captive female Eurasian lynx, Lynx lynx

Managing Population Sex Ratios in Conservation Practice: How and Why?

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