At least according to this article, most of the the protesters aren't Turkish.
A group of animal lovers, mostly foreign residents, will hold a protest march Saturday in Marmaris in the Muğla provice to protest animal killings in the region.
Many stray cats and dogs, as well as chickens and birds, have been poisoned in the last one-and-half months. Those responsible for distributing the poisoned food remain unidentified.
A 40-person animal lovers group that includes Turkish, English, Irish and Dutch volunteers, has organized a petition and a protest march to make their voices heard to the municipality.
They've organized a petition, and have about 1000 signatures so far. Marmaris Turkey is a big tourist destination, so maybe the bad publicity will force them to look into this.
I found this post about Marmaris on Care2's web site that I thought was interesting.
Hello! I'm new to Care2 and the group so I will introduce my self. My name is Daniela, I'm 36 yrs old and I'm from Holland. I have 7 cats, all of them have a "story" and I have 2 (stray-) guinnea pigs. The love for animals comes from my grandmother and mother. My sister and I grew up surrounded by all kinds of animals. Twice a year I go to Marmaris in Turkey and work in the shelter up in the mountains. The shelter is run by Jeannie Thirkill. She single handed put animal welfare on the agenda in Marmaris. In the shelter are appr. 300 cats, 2 dogs and a donkey. Jeannie also undertakes action to get the street cats neutered and spayed. During the winter she feeds the street cats of Marmaris. It is great to work in the shelter. I just love animals and to be surrounded by 300 cats is heaven for me. For some cats we find new homes in the UK, Holland, Germany, Belgium and Finland. This year I will be a foster mum for the cats who will go the UK. This is because of the quarantaine rules of the UK. I hope that we can make a positive change for all those animals in need!
Here's a link to the shelter.