Katherine Feng / Giant Panda (Ailuropoda melanoleuca) baby being weighed on a scale at the China Conservation and Research Center for the Giant Panda, Wolong Nature Reserve, China

Francisco Marquez / Volunteer weighing a Greater flamingo (Phoenicopterus ruber) juvenile while another volunteer notes the data during the ringing process, Fuente de Piedra lagoon, Malaga, Spain. August.

Francisco Marquez / Volunteer weighing a Greater flamingo (Phoenicopterus ruber) juvenile during the ringing process, Fuente de Piedra lagoon, Malaga, Spain. August.

Suzi Eszterhas / Striped Skunk (Mephitis mephitis) one month old orphaned babies being weighed, Sarvey Wildlife Care Center, Arlington, Washington

Edwin Giesbers / Eagle owl (Bubo bubo) chick on scales during ringing session. Netherlands. February 2016.

Edwin Giesbers / Man placing Eagle owl (Bubo bubo) chick on scales during ringing session. Netherlands. February 2016.

Edwin Giesbers / Man weighing Eagle owl (Bubo bubo) chick during ringing session. Netherlands. February 2016.

Suzi Eszterhas / Koala (Phascolarctos cinereus), male sick with chlamydia on scale while under anaesthetic. Currumbin Wildlife Hospital, Queensland, Australia, captive.

Suzi Eszterhas / Koala (Phascolarctos cinereus) Joey aged eight months, sick with urinary tract infection, on scales, Dreamland, Queensland, Australia, captive.

ZSSD / Jaguar (Panthera onca) cub being weighed, San Diego Zoo, California

Suzi Eszterhas / Virginia Opossum (Didelphis virginiana) twelve week old orphaned young on scale, WildCare, San Rafael, California

Suzi Eszterhas / Virginia Opossum (Didelphis virginiana) ten week old orphaned young on scale, WildCare, San Rafael, California