PEAK District dog walkers are asked to keep their pets on short leads to protect young farm animals and wildlife during the breeding season of spring and early summer.
Most responsible dog owners would be horrified if their pets injured newborn lambs or chicks but farmers have already reported such incidents in the Peak District National Park over the past few weeks.
Declining birds such as lapwing, curlew and snipe which nest on the ground are particularly vulnerable to harm from dogs roaming free or on long leads.
Tara Challoner, Peak District Wader Recovery Project officer said: "You may not always be aware that birds are present, which can easily lead you into thinking that the moors and fields are great empty places, perfect for letting your dog have a good run around.
"However many of these birds are in very serious trouble and we need to do all we can to ensure that they are not lost from our countryside forever."
Signs reminding people to keep their dogs under control have gone up on gates and stiles across the national park.
By law, dogs must be under control on public rights of way and on a short lead on open access land from March 1 to July 31. In fields containing farm animals and nesting birds it is sensible to keep dogs on a lead. National park ranger manager Jenny Waller said: "Walking a dog is one of the joys of the countryside, but we ask all dog-owners to think about young animals and keep their pets on short leads during this particularly sensitive time.
"Sheep and lambs can be badly injured or killed by uncontrolled dogs. For its own safety, never let a dog approach or chase farm animals or wildlife – your dog can get kicked, trampled or lost, and it could be legally shot for chasing farm animals.
"Cows will often defend their calves by turning on a dog. If that happens it's best to unclip the lead – a dog can usually look after itself – and get out of the field as quickly as possible, then call your dog as soon as you are out of danger.
"Legally, you do not have to use a lead on public paths, but you should be extra vigilant in the breeding season, and always use a lead if you can't rely on your dog's obedience."
Dogs are not allowed at all on some areas at certain times to protect sensitive breeding sites – signs will indicate this. To report incidents involving dogs on farmland or moors, call the police on 101. To ask for signs to go up in problem areas contact Peak District National Park rangers on 01629 816290 (weekdays).
For more advice read the Countryside Code at www.naturalengland.org.uk/countrysidecode