Precocial hindlimbs and altricial forelimbs: partitioning ontogenetic strategies in Mallard ducks(Anas platyrhynchos)

Abstract

SUMMARYPrecocial development, in which juveniles are relatively mature at hatching or birth, is more common among vertebrates than altricial development, and is likely to be the basal condition. Altricial development characterizes many birds and mammals and is generally viewed as an alternate strategy, promoting fast growth rates, short developmental periods and relatively poor locomotor performance prior to attaining adult size. Many aquatic birds such as Anseriformes (ducks, geese and swans), Charadriformes (gulls and terns) and Gruiformes (rails) undergo distinctive developmental trajectories, in that hatchlings are able to run and swim the day they hatch, yet they do not begin to fly until fully grown. We hypothesized that there should be tradeoffs in apportioning bone and muscle mass to the hindlimb and forelimb that could account for these patterns in locomotor behavior within the mallard (Anas platyrhynchos). Growth of the musculoskeletal system in the forelimbs and hindlimbs was measured and compared with maximal aquatic and terrestrial sprint speeds and aerial descent rates throughout the 2-month-long mallard ontogenetic period. At 30days post hatching, when body mass is 50% of adult values, hindlimb muscle mass averages 90% and forelimb muscle mass averages 10% of adult values; similarly, bone growth (length and width) in the hindlimbs and forelimbs averages 90 and 60% of adult values, respectively. The attainment of mallard locomotor performance parallels the morphological maturation of forelimb and hindlimb morphometrics -hindlimb performance initiates just after hatching at a relatively high level (~50% adult values) and gradually improves throughout the first month of development, while forelimb performance is relatively non-existent at hatching (~10% adult values), experiencing delayed and dramatic improvement in function, and maturing at the time of fledging. This divergence in ontogenetic strategy between locomotor modules could allow developing Anseriformes to inhabit aquatic, predator-reduced refuges without relying on flight for juvenile escape. Furthermore, by freeing the forelimbs from locomotor demand early in ontogeny, Anseriformes may bypass the potential canalization (i.e. retention) of juvenile form present within their precocial hindlimbs, to dramatically depart in forelimb form and function in the adult. Supplementary material available online at

Ontogeny of aerodynamics in Mallard ducks: comparative performance and developmental implications

“…Mallards reached an average terminal mass of ~1300g (Dial and Carrier, 2012) over a 60d.p.h. ontogenetic period, whereas previous work has shown that fully grown chukar average ~600g and develop for ~100d.p.h.…”

“…For chukar, day 8 corresponds well with the in vivo onset of lift during controlled flapping descent and WAIR (Tobalske and Dial, 2007;Jackson et al, 2009). However, flapping-descent experiments with mallards (Dial and Carrier, 2012) reveal that they do not produce significant lift in vivo until day 45 (supplementary material Fig. S3).…”

Aquatic burst locomotion by hydroplaning and paddling in common eiders (Somateria mollissima)

“…The bones and muscles of the wings of steamer ducks are considered to be stouter and more robust than those of flying birds (Lowe, 1934). Mallard ducklings also exhibit a wing-paddling behavior that is similar to steaming (Aigeldinger and Fish, 1995;Dial and Carrier, 2012). Like steamer ducks and eider ducks, mallard ducklings have high wing loadings, but in their case this is due to slow development of the wings relative to the precocial development of the hindlimbs (Dial and Carrier, 2012).…”

“…Mallard ducklings also exhibit a wing-paddling behavior that is similar to steaming (Aigeldinger and Fish, 1995;Dial and Carrier, 2012). Like steamer ducks and eider ducks, mallard ducklings have high wing loadings, but in their case this is due to slow development of the wings relative to the precocial development of the hindlimbs (Dial and Carrier, 2012). This wingpaddling behavior is most pronounced between day 30 and day 60 of their development, after which the wings are more fully developed and suited for flight (Dial and Carrier, 2012;.…”

Ontogeny of aerial righting and wing flapping in juvenile birds

“…One well-publicized example of ontogenetic change in avian wing function concerns the use by juvenile chukar and other taxa of symmetric flapping to assist in cursorial ascent of high-angle terrain (wing-assisted incline running or WAIR [8][9][10][11][12]). This behaviour, which in juvenile chukar occurs developmentally prior to full weight offset via powered flapping, has been proposed as a pathway for wing evolution in the theropod precursors to birds [8,9].…”