Nine ewes and 53 lambs worth £6,500 were stolen from one field near Thirsk between April 20 and 27, while 89 ewes were taken from a field near Leeming Bar on Tuesday, March 24.
Rural police officers say theft of livestock can cause farmers devastating financial losses, particularly during the coronavirus pandemic.
North Yorkshire Police are calling for heightened vigilance from the public, and for people to report any suspicious behaviour or activity in the countryside, particularly in the Hambleton and Ryedale areas.
Officers meanwhile are conducting regular patrols.
Inspector Matt Hagen, who heads North Yorkshire Police’s rural taskforce, said: Farmers are doing their best to make a living and keep food on our tables in these difficult times - so having livestock stolen is the last thing they need.”
Some £2.5m worth of farm animals were stolen nationwide in 2018, according to NFU Mutual.
Criminals may steal livestock for slaughter, prompting fears around unnecessary cruelty and that the meat may enter the human food chain. Livestock thefts have also been linked to organised crime gangs.
Other recent instances of livestock theft have included a female goat worth £100 which was stolen from a field near Pickering overnight between April 22 and 23, while earlier this year 88 piglets were stolen from a farm near Helmsley. The theft of the piglets, which was only discovered last month during a count, would have cost the farmer approximately £3,800.
Farmers are being urged to ensure all stock is clearly marked and keep animals in fields away from roads where possible.
Livestock should also be counted regularly with feeding and check-up times varied.
Insp Hagen added: “Livestock theft can be devastating for farmers and their businesses, as well as causing unnecessary suffering to animals.
“If you think you have been a victim, or you have any information about who is committing these crimes, please call us. We take all reports extremely seriously as we work to keep these criminals away from North Yorkshire’s farms.”