Debra S Judge

Publications (30) View all

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  Available from: Debra S Judge

  Article: Embryonic And Juvenile Attachment Structures In Cherax Cainii (decapoda: Parastacidae): Implications For Maternal Care

  TIM BURTON, BRENTON KNOTT, DEBRA JUDGE, PHIL VERCOE, ANNE BREARLEY
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  ABSTRACT: Fertilised eggs, stage one and stage two juveniles of the smooth marron, Cherax cainii, are attached to the pleopods of the gravid female via specialised structures. The eggs are fixed to the maternal pleopods by egg stalks, whereas stage one and stage two juveniles remain attached by recurved spines on the dactyls of their fourth and fifth pereopods. Crayfish of the third juvenile stage are independent of the mother and receive no maternal care; their dactyl spines are straight and cannot grasp the mother's pleopods; the female displays agonistic behaviour toward her young commencing with stage III instars. We suggest that eggs and the first two juvenile stages attached to the mother would experience reduced levels of predation and be secured against strong river flow. We conclude by reviewing, briefly, the potential fitness costs and benefits of maternal care, to the mother and young of freshwater crayfish, from a life-history perspective.
  American Midland Naturalist 01/2009; · 0.62 Impact Factor
• Article: Singing by male and female Kloss gibbons (Hylobates klossii) in the Peleonan Forest, Siberut Island, Indonesia.

  Helen M Dooley, Debra S Judge, Lincoln H Schmitt
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  ABSTRACT: Kloss gibbons (Hylobates klossii) are endemic to the Mentawai Islands in Indonesia and are one of only two gibbon species in which mated pairs do not sing duets. This is the first long-term study of the factors influencing the singing activity of Kloss gibbons within a northern Siberut Island population and follows two previous studies in central Siberut nearly 30 years ago. We collected data on the presence/absence of male and female singing within the study area on 198 days and within a focal group on 47 days. Rainfall during the time period in which they normally sing inhibits singing in both males and females. Our study supports the hypothesis that male and female songs function in intrasexual resource defence, as singing is associated with singing by same-sex neighbours, and same-sex choruses are more likely to occur after one or more days of silence (from that sex), suggesting there is pressure for individuals to communicate with same-sex neighbours regularly. Singing was not coordinated within a mated pair, suggesting that vocal coordination of the pair has been lost with the loss of the duet and that Kloss gibbon songs do not convey information to neighbours about the strength of the pair bond. On days when males sang predawn, females were more likely to sing after dawn and earlier in the morning. Additionally, the number of groups singing in female choruses was positively associated with the number of males that had sung in the predawn male chorus. We suggest that female songs have an intersexual territory defence as well as an intrasexual function.
  Primates 01/2013; 54(1):39-48. · 1.40 Impact Factor
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  Available from: Debra S Judge

  Article: A Novel Quantitative Approach to Women's Reproductive Strategies

  Fritha H Milne, Debra S Judge
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  ABSTRACT: The patterned way in which individuals allocate finite resources to various components of reproduction (e.g. mating effort, reproductive timing and parental investment) is described as a reproductive strategy. As energy is limited, trade-offs between and within aspects of reproductive strategies are expected. The first aim of this study was to derive aspects of reproductive strategies using complete reproductive histories from 718 parous Western Australian women. Factor analysis using a subset of these participants resulted in six factors that represented 'short-term mating strategy', 'early onset of sexual activity', 'reproductive output', 'timing of childbearing', 'breastfeeding', and 'child spacing'. This factor structure was internally validated by replication using a second independent subset of the data. The second aim of this study examined trade-offs between aspects of reproductive strategies derived from aim one. Factor scores calculated for each woman were incorporated in generalised linear models and interaction terms were employed to examine the effect of mating behaviour on the relationships between reproductive timing, parental investment and overall reproductive success. Early sexual activity correlates with early reproductive onset for women displaying more long-term mating strategies. Women with more short-term mating strategies exhibit a trade-off between child quantity and child quality not observed in women with a long-term mating strategy. However, women with a short-term mating strategy who delay reproductive timing exhibit levels of parental investment (measured as breastfeeding duration per child) similar to that of women with long-term mating strategies. Reproductive delay has fitness costs (fewer births) for women displaying more short-term mating strategies. We provide empirical evidence that reproductive histories of contemporary women reflect aspects of reproductive strategies, and associations between these strategic elements, as predicted from life history theory. Citation: Milne FH, Judge DS (2012) A Novel Quantitative Approach to Women's Reproductive Strategies. PLoS ONE 7(10): e46760. Copyright: ß 2012 Milne, Judge. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
  PLoS ONE 10/2012; · 4.09 Impact Factor
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  Available from: Debra S Judge

  Article: Vocal responses of captive gibbon groups to a mate change in a pair of white-cheeked gibbons (Nomascus leucogenys).

  Helen Dooley, Debra Judge
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  ABSTRACT: The singing behaviour of 3 pairs of white-cheeked gibbons (Nomascus leucogenys) held at the Perth Zoo was observed for 6 months in 2005. These groups included a family (mated pair and 2 immature offspring) and a pair without offspring. During the study, the female without offspring was exchanged for an unpaired female from New Zealand. After the new pair had been released onto the island enclosure and began to duet, the duetting rate of the white-cheeked gibbon family increased. The increased singing began after the new female had started to sing solo female great calls. These observations support the hypothesis that duets have an intergroup communication function in white-cheeked gibbons. The pair that duetted most frequently also copulated most frequently but allogroomed the least. We suggest that duetting may be more important to intergroup relations than to pair bond maintenance in this species.
  Folia Primatologica 02/2007; 78(4):228-39. · 1.00 Impact Factor
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  Available from: Debra S Judge

  Article: Life Span Extension in Humans Is Self-Reinforcing: A General Theory of Longevity

  James R. Carey, Debra S. Judge
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  ABSTRACT: This article proposes that longevity is not merely the result of an absence of mortality but a self-reinforcing and positively selected life-history trait in social species. It argues that a small increase in longevity is amplified as (1) reductions in mortality at young ages increase natural selection for mechanisms of maintenance and repair at all older ages as well as increasing the potential for intergenerational transfers; (2) intergenera-tional transfers of resources from old to young increase fitness (e.g., through improved health, skill, and competitive ability) of the young and thus favor the presence of older individuals in a population; and (3) the division of labor increases both efficiency and innovation at all levels, resulting in increased resources that can be reinvested. This theory is framed around the longevity-oriented question posed two decades ago by the ger-ontologist George Sacher, "Why do we live as long as we do?," rather than the more prevalent question today, "Why do we grow old?" The article describes the foundational principles and the main phases of a model for the evolution of longevity mediated through social organization, and applies the concept specifically to human populations. Copyright 2001 by The Population Council, Inc..
  Population and Development Review 02/2001; 27(3):411-436. · 2.22 Impact Factor