693 names here end in -s, and of the ones with a recorded sex, 330 measure male against 92 female. The reason is not the sound. It is where the names came from before they were pet names.
Mostly classical, by way of people
159 of the slice are names a dictionary lists for a person, and those average 168 registrations against 66 for the ending as a whole. Atlas, Gus, Zeus, Marcus. The masculine nominative in Greek and Latin ended in -s, and a dog is called Atlas today as a consequence of a grammar nobody has spoken in centuries.
It closes hard, and that is the useful part
148 are single syllables and 429 have two. An -s is a stop you can hear at distance: it does not trail off, it hisses and finishes. That is the opposite property to a lifting -y, and it suits a name you expect to call rather than coo.
Which brings a problem worth checking
A short name ending in a sibilant sits close to sit and stay in the mouth, and close enough matters when an animal is learning the name and the cues in the same fortnight. Read your shortlist aloud against the words you intend to train with. This site keeps a separate page on names that clash with commands, and this ending supplies a good share of them.
Is -s a male ending for pet names?
In these registers it reads that way: 330 male against 92 female. It comes from the classical masculine nominative rather than from anything about the sound.
Why do so many pet names end in -s?
Most of them are people's names first — 159 of the 693 are dictionary-listed given names, and they average 168 registrations against 66 for the ending generally.
Do -s names cause training problems?
The registers cannot measure that. What they show is that 148 of these are single syllables, which is the shape most closely matching a spoken cue, so it is worth reading the shortlist aloud against your commands.
Every count on this site is a tally of real registrations: pet licences and shelter intakes published as open data by New York, Seattle, Austin, Montgomery County, Cambridge, Zurich, Basel and four Australian councils. Popularity here is the average share a name holds across those registers, so a name common in a small city is not buried by one common in a large one. Five of the eleven registers are North American and they supply 86% of the records, so read the ordering as naming in those places rather than worldwide. Browse the whole catalogue or read how the data is put together.