Introduction
Captive animal phenotypes can diverge from the ideal ‘wild type’, and
these changes can affect behavior, morphology and physiology (Crates et al. 2022). However, the specific nature and combination of
‘captive phenotypes’ can vary widely between species (Crates et
al. 2022). Whether changes are important depends on the intended use of
captive-bred animals. For display animals, phenotypic changes may be
inconsequential. Conversely, conservation breeding programs – a
globally popular tool to combat species extinctions (Conde et al.2011) – should ideally produce animals optimized for life in the wild
after release, but this more easily said than done (Taylor et al.2017). If altered captive phenotypes incur a fitness cost in the wild,
conservation breeding may be less effective than hoped (Crates et
al. 2022). Thus, it is important that conservation breeding programs
quantify optimal wild phenotypes, and be vigilant of changes arising
from life in captivity that might jeopardize survival after release
(Shier 2016; Berger-Tal et al. 2020).
Phenotypic changes to traits involved in strenuous or high-risk phases
of life history may be disproportionately important for fitness post
release from captivity. For example, migration is a high-risk behavior
that strongly selects for the most capable individuals (Dingle 2014;
Rotics et al. 2016). Captive-born animals are often less
successful migrants than wild-born conspecifics (Crates et al.2022). This is sometimes attributable to behavioral differences. For
example, some captive-born birds depart later and travel shorter
distances than wild conspecifics (Burnside et al. 2017), and
captive-bred butterflies fail to orient themselves or even attempt
migration (Tenger-Trolander et al. 2019). Morphological changes
also likely contribute to poor migration outcomes post release, but
evidence for their effects on fitness is surprisingly limited. Davis et
al. (2020) recently showed that captive-bred monarch butterflies Danaus plexippus have differently shaped wings and lower
migration success than wild conspecifics. Wing shape strongly predicts
flight efficiency (Lockwood et al. 1998; Sheard et al.2020). Given that migratory birds are commonly bred in captivity for
reintroduction (Davis 2010; Burnside et al. 2017; Hutchins et al. 2018; Stojanovic et al. 2020b; Tripovich et
al. 2021), quantifying the ubiquity of deleterious captive wing shape
phenotypes and their post-release fitness consequences is critical
information.
I aimed first to compare captive/wild wings of 16 species representing
three commonly captive-bred bird families (Phasianidae, Psittacidae,
Estrildidae) to evaluate the ubiquity of captive wing shape phenotypes.
Then, using a critically endangered migratory bird as a model, I aimed
to demonstrate that a captive wing shape phenotype incurs a fitness cost
post release.