Late last year I happened to read two very enjoyable crime novels in which the lead characters were vegetarian. I put a call out to Sharon at Crime Review UK/Two Fat Vegetarians as to whether she could think of any more vegetarian detectives and she circulated the request more widely. However we pretty much drew a blank. So here are the handful that we've discovered and I would love to know of more, and of course any corrections. I'm including the US in this list to make it a bit longer!
The two I read which prompted this post are:
1. The Mangle Street Murders (2013) by M R C Kasasian which introduces Sidney Grice and his ward March Middleton. Sidney Grice is a vegan. I loved this book and my full review is here.
2. Paws for Murder (2014) by Annie Knox which is also the first in a new series. The main character, Izzy, and her best friend Rena, are both vegetarians. I reviewed it here.
UK Vegetarian Sleuths
Cath Staincliffe's's Manchester PI Sal Kilkenny is vegetarian at least in the early books. I believe she may have changed in the newer ones. The first book in the series is Looking for Trouble (1994).
DS Annie Cabbot first appeared in In a Dry Season (1999), the tenth in the Inspector Banks series by Peter Robinson. I believe Annie wobbles a bit on the path of true vegetarianism but is pretty close.
Added May 2018:
US Vegetarian Sleuths
In the currently fifteen-book series which began with The Monkey's Raincoat (1987), it's Robert Crais's Joe Pike, sidekick to Elvis Cole, and sometimes centre-stage protagonist who is vegetarian.
Harlan Coben's Myron Bolitar has a vegetarian one-man killing machine sidekick called Win. The first book in the series is Deal Breaker (1995).
Judy Fitzwater's six-book (soon to be seven) series features aspiring crime novelist and vegetarian Jennifer Marsh. The first book, Dying to Get Published (1995), is currently free as an ebook.
Jaqueline Girdner wrote a twelve-book series about Californian vegetarian Kate Jasper which began with, Adjusted to Death (1990).
Jaqueline Girdner also wrote a four-book series as Claire Daniels about a holistic healer. The first book is Body of Intuition (2002). I am assuming these also feature a vegetarian sleuth.
Added May 2018:
Golden Age writer, Victor L Whitechurch wrote a number of short stories featuring Thorpe Hazell - "vegetarian, detective and expert in all aspects of the railway" and at least some of these have made available on Kindle by Black Heath Editions. See comments section for more information.