I was reading Tom Holland’s excellent Rubicon: The Last Years of the Roman Republic when Holland mentions in passing an annual ritual that the Romans apparently carried out almost until the very end of what we would recognize as Rome,
Every year guard-dogs would be crucified, a posthumous punishment of the dogs who had failed to bark on the Capitol, while Juno’s geese, as an ongoing reward for their ancestors’ admonitory honking, were brought to watch the spectacle on cushions of purple and gold.
Okay, that is messed up, which meant I had to know more. The annual ritual was known as Supplicia Canum and, according to Wikipedia, is mentioned by at least seven separate ancient authors.
Sources mentioning the ritual agree that the “punishment” was inflicted on the dogs for their failure to warn the Romans of the stealth attack against the citadel by the Gauls during the Gallic siege of Rome in 390 BC (or 387). Legends vary regarding this historical event—the only sack of the city during the Republican era—but in the sources that allude to the supplicia canum, temple geese are said to have raised the alarm instead. Plutarch and Aelian rationalize the dogs’ failure by explaining that the Gauls fed the siege-starved dogs and silenced them, while the geese called out excitedly. In recognition of this service, for the supplicia procession geese were decked out in purple and gold, then carried on a litter. The August 3 date, however, is hard to account for within the traditional chronology that had the Gauls setting fire to the city on July 19 and maintaining a siege through February.
Wikipedia cites a reference to geese being maintained for the ritual into the 4th century, though apparently no mention of whether or not the dog sacrifice portion of the Supplicia was still observed.