Fewer than one in 10 people convicted of animal cruelty offences in Wales in the last decade have been jailed, research by BBC Wales shows.
Last year, a man from Caerphilly avoided jail after he was convicted of having sex with his two dogs.
The maximum custodial sentence for animal cruelty in England and Wales - six months - is the lowest in Europe.
Magistrates "treat each individual case on its merits", the chairman of the Magistrates' Association said.
Just 102 of the 1,268 convictions for animal cruelty offences in courts in Wales - 8% - resulted in a custodial sentence between 2007 and 2017, an analysis of Ministry of Justice figures reveals.
And there has been a significant decline in the number of custodial sentences issued by courts in Wales - from a peak of 17 in 2011, to just six in 2017 - despite animal cruelty cases being at a five-year high.
Responding to the figures, the RSPCA has called for tougher sentencing. But the BBC has found that only two maximum six-month sentences were issued by Welsh courts in the past decade.
'Disgusting and horrific'
A Caerphilly man who was caught having sex with his two dogs avoided prison and was banned from keeping animals for 10 years.
Robert Gwynn, 60, received a three-month suspended sentence last May after his neighbours witnessed the him committing the "disgusting and horrific" acts against his own dogs, Taff and Ben.
In another case prosecuted by the RSPCA, a Merthyr Tydfil cat owner spoke of his horror when he discovered CCTV footage of his cat being intentionally set upon and mauled to death by a dog.
Two boys, aged 15 and 17, were sentenced to a 12-month referral order to the youth offending team and were banned from keeping animals for 10 years after admitting causing unnecessary suffering.
Cases such as these have led the RSPCA to call for tougher sentencing powers for magistrates to act as a stronger deterrent.
"Though custodial sentences are comparatively rare for animal-related offences, it is vital magistrates have at their disposal stronger sentences to send a clear statement to those thinking of harming animals that this behaviour will not be tolerated," said Michael Flower, the RSPCA's deputy head of prosecutions.
The majority of custodial sentences (44%) were one month or less in length. Almost a third were more than three months but less than the maximum six months.
In Scotland, the maximum sentence is 12 months but the Scottish Government is consulting on whether to increase this to five years. The maximum sentence in Northern Ireland is five years.
A 2017 survey by Battersea Dogs and Cats Home found 65% of the public agreed with increasing the maximum custodial sentencing powers of courts dealing with animal cruelty cases.
The UK government, which has previously committed to increase the maximum sentence from six months to five years, said it will do so "as soon as parliamentary time allows" to make the UK "a world leader in the care and protection of animals".
The BBC has found that only two maximum six-month jail sentences were handed down by courts in Wales between 2007 and 2017, raising the question whether tougher sentencing would make a difference.
The body which represents magistrates in the UK claims it would.
"Magistrates always treat each individual case on its merits and sentence in line with the law and appropriate sentencing guidelines," said John Bache, chairman of the Magistrates' Association.
"Maximum sentences are set by parliament, not the judiciary, but if they are increased this will change the range of sentences available and therefore affect sentencing guidelines and sentencing practice."
Animal welfare is a devolved matter, but justice is not - meaning there has been some confusion over whether the Welsh Government has the power to introduce tougher sentencing.
The Welsh Government said it supports the UK government legislating to increase the maximum sentence to five years in England and Wales.
"We have decided maintaining a comparative sentencing regime was important to ensure clarity for enforcement agencies, the courts and the public alike," a spokesperson added.