All the animals at Whipsnade Zoo in Bedfordshire, from little lemurs to enormous elephants, are being weighed and measured in an annual survey.
It's a huge task for keepers as they began the task of cataloguing each one of its 2,500 animals. The heights and weights of 200 species are being recorded.
Click below to watch a report by ITV News Anglia's Claire McGlasson
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A dry night with broken cloud and occasional clear spells. Generally cloudy with occasional outbreaks of rain during Thursday morning.