It has been happening since the first fences went up around cleared paddocks and the first flocks of sheep introduced to them.
Losses which were, effectively, simply written off.
But over the past few years it appears to have ramped up to a disturbing new level.
As Matapiro farmer Anthea Yule told me a couple of days ago - it is organised and it is getting more serious by the day.
She expects to lose up to 200 stock to thieves every year and she's not the only Bay farmer having to deal with it.
There has been a string of recent incidents and the numbers, in terms of what is going missing during a single rustling strike, are growing.
When thieves start taking 10 or 20 at a time then they have bigger plans in mind than just filling a fridge.
But whether it is 20 or just one, theft is theft, and in the long run that is one or 20 sheep the farmer will have to replace.
So it's a loss of around $200 - for a lost sale and the need to buy another one.
The cockies of Hawke's Bay have had a wretched run over the past year with the drought hammering their land, their stock, their livelihoods and their lives.
Now they are being increasingly targeted by rustlers who are seeking to save money, or make money, at the expense of people who are desperately trying to get themselves and, in the long run, our economy back on track.
What can be done?
Keep an ear to the ground.
Heard about some lamb going cheap?
Heard about some "hard case dudes" grabbing some sheep the other night?
Call it in. Call the police.
Theft is theft ... bring the cowboys to justice.