title: Variation in growth of Damaraland mole-rats is explained by competition rather than by functional specialization for different tasks.
abstract: In some eusocial insect societies, adaptation to the division of labour results in multimodal size variation among workers. It has been suggested that variation in size and growth among non-breeders in naked and Damaraland mole-rats may similarly reflect functional divergence associated with different cooperative tasks. However, it is unclear whether individual growth rates are multimodally distributed (as would be expected if variation in growth is associated with specialization for different tasks) or whether variation in growth is unimodally distributed, and is related to differences in the social and physical environment (as would be predicted if there are individual differences in growth but no discrete differences in developmental pathways). Here, we show that growth trajectories of non-breeding Damaraland mole-rats vary widely, and that their distribution is unimodal, contrary to the suggestion that variation in growth is the result of differentiation into discrete castes. Though there is no evidence of discrete variation in growth, social factors appear to exert important effects on growth rates and age-specific size, which are both reduced in large social groups.
authors.affiliation: Department of Zoology, University of Cambridge, Cambridge, UK mz338@cam.ac.uk.
authors.forename: Markus
authors.identifier: 0000-0002-5582-2306
authors.initials: M
authors.lastname: Zöttl
authors.affiliation: Department of Zoology, University of Cambridge, Cambridge, UK.
authors.forename: Jack
authors.identifier: 0000-0002-8426-610X
authors.initials: J
authors.lastname: Thorley
authors.affiliation: Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa.
authors.forename: David
authors.initials: D
authors.lastname: Gaynor
authors.affiliation: Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa.
authors.forename: Nigel C
authors.initials: NC
authors.lastname: Bennett
authors.affiliation: Department of Zoology, University of Cambridge, Cambridge, UK.|Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa.
authors.forename: Tim
authors.initials: T
authors.lastname: Clutton-Brock
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D001835:Body Weight; D003163:Competitive Behavior; D005260:Female; D008297:Male; D019577:Mole Rats / Q000254:growth & development* / Q000502:physiology / Q000523:psychology; D012737:Sex Factors; D012919:Social Behavior
keywords: cooperative breeding; division of labour; eusociality; growth