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Penguins 211

By day 50–60, chicks are fed larger whole fishes, cautiously, to satiation twice daily. Continue to
weigh and monitor intake through introduction to the colony. It is normal for chicks approaching
fledging to self‐regulate food intake intermittently.
Parent‐reared chicks removed for hand ‐earing should be transitioned to the diet based on weight
and health status. Chicks >21 days old may not need formula and may be fed initially with small
whole fish. For chicks receiving formula, it is advisable to test syringe‐feeding with warm water,
then transition briefly through formula dilutions prior to giving undiluted formula per feeding
guidelines.

­ Expected­Weight­Gain

Penguin chick weight gain expectations vary with age and stage. Growth rates for hand‐reared
chicks are slightly slower than those of parent‐reared chicks. Hand‐reared chicks typically lose
weight for the first 1–3 days or until undiluted formula is introduced, then gain 5–15% of their body
weight daily thereafter. Weight gains escalate after 7 days until about 21–30 days (species depend-
ent) when weight gains slow to 5–10% daily. Growth rate graphs for several species are available in
Appendix I of the Penguin Husbandry Manual (Henry and Sirpenski 2005).
Most parent‐reared chicks will double their hatch weight within the first 5–7 days, and weekly
weights taken through 21 days reflect weights 1.5–2 times the previous week’s weight. Thereafter,
weight gains slow slightly until fledging. Hand‐reared and parent‐reared chicks share similar
fledging and 1‐year weight trends.

­ Housing

Housing should be set up 2 weeks prior to the expected first chick and monitored for temperature
stability. Penguins do best in a low‐humidity, moving‐air environment. Open‐top brooders with
heat lamps or Animal Intensive Care units (AICU) without water added are recommended.
Substrate for neonates should be irregular, such as toweling set over a bed of river rocks or upside‐
down Dri‐Dek tile. Later, bins or floor areas lined with river rock (2.5–3 in./5.1–7.6 cm size) are
appropriate for chicks in the post‐guard stage. Where feasible, chicks removed for habituation and
hand‐reared chicks aged >21–30 days should be housed separately within the main penguin habi-
tat, within visual and vocal proximity of the colony.
Temperature regulation is vital to penguin chick‐rearing success. While 1–3‐day old chicks may
need to be kept very warm, chick access to a temperature gradient in the brooder by days 5–7 will
improve outcomes. Temperature needs of chicks change daily. Vigilance is necessary to avoid ill-
ness resulting from overheating. Signs of overheating include outspread extremities, difficulty
waking up, weak or absent feeding response, lethargy, and/or panting. Moderately overheated
chicks may show no behavioral signs other than refusing to finish all food offered. Shivering does
not necessarily indicate a need for additional heat. Chicks use shivering to maintain and develop
thermoregulation and it may also be observed immediately following a feeding. Penguin chicks
tolerate cooling better than overheating; however, young chicks can become chilled. Rearing two
to four chicks together will allow them to huddle for warmth.
A small, warmed rice bag may serve to provide temporary warmth for guard‐stage chicks with-
out modifying brooder temperatures. Overheated crèche‐phase chicks can benefit from standing
®
on a towel‐covered frozen BlueIce block.