A panda cub named Xiangxiang is seen during a health check at Tokyo's Ueno Zoological Gardens. /VCG Photo 

A freshwater stingray is being measured during the annual inventory at the Sea Life aquarium in Hanover, northern Germany. /VCG Photo

The gorillas are tricked into being measured by peanut butter and cabbages hidden behind the ruler. /VCG Photo

The two lions are attracted by some meat on a measuring stick during the annual inventory at the zoo in Hanover, Northern Germany. /VCG Photo

The keeper checks the hippos' teeth by throwing food to them. /VCG Photo

A zookeeper holds a giant stick insect during the London Zoo annual weigh-in. /VCG Photo

A penguin steps on scales during a photocall for the annual weigh-in at London Zoo. /VCG Photo

A one-month-old lion cub is undergoing an X-ray check. /VCG Photo

Zookeepers measure the length of a Pueblan milk snake in the Reptile House of ZSL London Zoo. /VCG Photo

Keepers at ZSL Whipsnade Zoo are seen giving eight-week-old endangered tiger cubs their first health checks with vets. /VCG Photo

A frog sits on a scale. /VCG Photo

A zookeeper weighs meerkat during the annual weigh-in at ZSL London Zoo. /VCG Photo 

An Iberian midwife toad is measured during a photocall at London Zoo. /VCG Photo

Zookeeper is brushing teeth for a hippo at a zoo in Xiamen, China. /VCG Photo

Zookeeper Jeff Lambert measures Jacqueline, a Mexican red-kneed tarantula, at ZSL London Zoo. /VCG Photo