Dog owners need to be more responsible to reduce the number of strays being picked up in Darlington, council bosses have said.
Darlington Council said 517 stray dogs had been collected in the town between April 2009 and April 2010 - 55 more than the previous 12-month period.
Officials have urged people to get their pets microchipped to make it easier to trace owners.
A spokesman said the increasing workload was a strain on resources.
He said dog wardens were picking up an average of 43 stray pets a month.
Since 2008 police in England and Wales are no longer responsible for stray dogs.