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Adoption in eastern grey kangaroos: a consequence of misdirected care?

King WJ, Forsyth DM, Coulson G, Festa-Bianchet M - PLoS ONE (2015)

Bottom Line: Switch mothers did not associate closely.Adoption did not improve juvenile survival.We conclude that adoptions in this wild population were potentially costly and likely caused by misdirected care, suggesting that eastern grey kangaroos may have poorly developed mother-offspring recognition mechanisms.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, University of Queensland, St. Lucia, Queensland, Australia.

ABSTRACT
Adoption is rare in animals and is usually attributed to kin selection. In a 6-year study of eastern grey kangaroos (Macropus giganteus), 11 of 326 juveniles were adopted. We detected eight adoptions by observing behavioural associations and nursing between marked mothers and young and three more by analysing the relatedness of mothers and young using microsatellite DNA. Four adoptions involved reciprocal switches and three were by mothers whose own pouch young were known to subsequently disappear. Adoptive mothers were not closely related to each other or to adoptees but adoptive mothers and young associated as closely as did biological pairs, as measured by half-weight indices. Switch mothers did not associate closely. Maternal age and body condition did not influence the likelihood of adoption but females were more likely to adopt in years with high densities of females with large pouch young. Adoption did not improve juvenile survival. We conclude that adoptions in this wild population were potentially costly and likely caused by misdirected care, suggesting that eastern grey kangaroos may have poorly developed mother-offspring recognition mechanisms.

No MeSH data available.


Related in: MedlinePlus

Female #81 with adopted young #531 in her pouch.The light blue eartag in the ear of #531 was applied when captured in the pouch of female #363. Photo courtesy of C. Le Gall-Payne.
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pone.0125182.g001: Female #81 with adopted young #531 in her pouch.The light blue eartag in the ear of #531 was applied when captured in the pouch of female #363. Photo courtesy of C. Le Gall-Payne.

Mentions: We initially detected adoptions through observations of associations, pouch occupation and nursing between marked mothers and young (see Fig 1). To assess the effects of maternal age, body condition and population density on the likelihood of adoption and juvenile survival, we compared those factors for the 11 adoptive females for the year they adopted to all other years they were monitored (range 2–5 years). We fitted generalised linear mixed-effect logistic regressions with binomial errors in R version 2.15.2 [25], using maternal identity as a random factor. We sequentially removed the least significant parameter (based on its P-value, threshold ≥0.05) from models using stepwise backward selection [26]. Predictors for whether females adopted included age class, body condition, winter density of females with large pouch young and all 2-way interactions. Predictors for juvenile survival also included whether the offspring had been adopted. We did not include parity in analyses because it was correlated with age (all primiparous females were young) and was unknown at first capture. We compared the proportion of adoptive females that successfully raised an offspring to the large pouch young stage in the year following an adoption to the population average using a Fisher Exact Test. Intensive observations (approximately 45 h/month) from April 2010 to June 2012 allowed assessment of mother-offspring associations using half-weight indices (HWIs) calculated in SOCPROG 2.4 [27]. HWIs measure the proportion of time individuals are seen together in the same group [27] and we defined a group using the 10-m chain rule [28]. We compared 4-month HWIs between mothers and adopted young to those between mothers and biological offspring using t-tests. We also calculated HWIs between adoptive and biological mothers (if both individuals were known) from intensive observations taken in August through November 2010–2013. We investigated genetic relationships using 9 highly polymorphic microsatellite markers (G12-6, G16-1, G16-2, G19-1, G26-4, G31-1, G31-3, T3-1T and T32-1) [29,30], according to the methods of King et al. [31] and calculated pairwise relatedness (r) using KINGROUP v2 [32]. Mothers and putative young with mismatched genotypes without behavioural data on adoption were re-sampled and re-analysed for verification of non-relatedness. Spreadsheets of (1) characteristics of adoptive mothers and offspring survival for all years monitored, (2) genotypes of adoptive mothers and offspring and (3) HWIs of mothers with offspring are available at Dryad Digital Depository, http://dx.doi.org/10.5061/dryad.jr531.


Adoption in eastern grey kangaroos: a consequence of misdirected care?

King WJ, Forsyth DM, Coulson G, Festa-Bianchet M - PLoS ONE (2015)

Female #81 with adopted young #531 in her pouch.The light blue eartag in the ear of #531 was applied when captured in the pouch of female #363. Photo courtesy of C. Le Gall-Payne.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4430339&req=5

pone.0125182.g001: Female #81 with adopted young #531 in her pouch.The light blue eartag in the ear of #531 was applied when captured in the pouch of female #363. Photo courtesy of C. Le Gall-Payne.
Mentions: We initially detected adoptions through observations of associations, pouch occupation and nursing between marked mothers and young (see Fig 1). To assess the effects of maternal age, body condition and population density on the likelihood of adoption and juvenile survival, we compared those factors for the 11 adoptive females for the year they adopted to all other years they were monitored (range 2–5 years). We fitted generalised linear mixed-effect logistic regressions with binomial errors in R version 2.15.2 [25], using maternal identity as a random factor. We sequentially removed the least significant parameter (based on its P-value, threshold ≥0.05) from models using stepwise backward selection [26]. Predictors for whether females adopted included age class, body condition, winter density of females with large pouch young and all 2-way interactions. Predictors for juvenile survival also included whether the offspring had been adopted. We did not include parity in analyses because it was correlated with age (all primiparous females were young) and was unknown at first capture. We compared the proportion of adoptive females that successfully raised an offspring to the large pouch young stage in the year following an adoption to the population average using a Fisher Exact Test. Intensive observations (approximately 45 h/month) from April 2010 to June 2012 allowed assessment of mother-offspring associations using half-weight indices (HWIs) calculated in SOCPROG 2.4 [27]. HWIs measure the proportion of time individuals are seen together in the same group [27] and we defined a group using the 10-m chain rule [28]. We compared 4-month HWIs between mothers and adopted young to those between mothers and biological offspring using t-tests. We also calculated HWIs between adoptive and biological mothers (if both individuals were known) from intensive observations taken in August through November 2010–2013. We investigated genetic relationships using 9 highly polymorphic microsatellite markers (G12-6, G16-1, G16-2, G19-1, G26-4, G31-1, G31-3, T3-1T and T32-1) [29,30], according to the methods of King et al. [31] and calculated pairwise relatedness (r) using KINGROUP v2 [32]. Mothers and putative young with mismatched genotypes without behavioural data on adoption were re-sampled and re-analysed for verification of non-relatedness. Spreadsheets of (1) characteristics of adoptive mothers and offspring survival for all years monitored, (2) genotypes of adoptive mothers and offspring and (3) HWIs of mothers with offspring are available at Dryad Digital Depository, http://dx.doi.org/10.5061/dryad.jr531.

Bottom Line: Switch mothers did not associate closely.Adoption did not improve juvenile survival.We conclude that adoptions in this wild population were potentially costly and likely caused by misdirected care, suggesting that eastern grey kangaroos may have poorly developed mother-offspring recognition mechanisms.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, University of Queensland, St. Lucia, Queensland, Australia.

ABSTRACT
Adoption is rare in animals and is usually attributed to kin selection. In a 6-year study of eastern grey kangaroos (Macropus giganteus), 11 of 326 juveniles were adopted. We detected eight adoptions by observing behavioural associations and nursing between marked mothers and young and three more by analysing the relatedness of mothers and young using microsatellite DNA. Four adoptions involved reciprocal switches and three were by mothers whose own pouch young were known to subsequently disappear. Adoptive mothers were not closely related to each other or to adoptees but adoptive mothers and young associated as closely as did biological pairs, as measured by half-weight indices. Switch mothers did not associate closely. Maternal age and body condition did not influence the likelihood of adoption but females were more likely to adopt in years with high densities of females with large pouch young. Adoption did not improve juvenile survival. We conclude that adoptions in this wild population were potentially costly and likely caused by misdirected care, suggesting that eastern grey kangaroos may have poorly developed mother-offspring recognition mechanisms.

No MeSH data available.


Related in: MedlinePlus