The National Zoological Park's only monitor lizards are the latest casualty. Apart from these, spotted deer, water birds, a baby gibbon and grey partridge birds were some of the recent deaths reported at the zoo.

"We have also lost many popular animals like giraffe, zebra, ostrich, king cobra, etc. in the recent past due to various reasons. It is very unfortunate. Many visitors have complained that they do not find enough animals here," a zoo official said.

The enclosures of ostrich, giraffe, zebra, monitor lizards, king cobra, etc. have been lying vacant for quite some time. The zoo had lost around 46 spotted deer last year and a few brow-antlered deer.

According to the zoo authorities, these animals died of 'natural' causes.

However, sources in the zoo have put the blame on the authorities, alleging that they had failed to take good care of the animals.

Noting that the decreasing number of inmates is a worrying trend, they maintained that the zoo was in dire need of revamping its exchange programmes.

"We are hoping that we will have some animals to attract the people after the zoo exchange programmes are sanctioned by the higher-ups," an official said.

The Delhi zoo will release its annual inventory report next month.