I have heard Lord Buddha has taught a special version of meththa for certain kind of creatures.
Can someone point reference to such a teaching in suttas?
The sutta Chris W had mentioned above has a chanting of its own in theravada tradition.It is called "Bandha Piritha". Here's the full translation of it.
I heard this way....
Once Lord Buddha was residing in the Jethavana Monastery of noble Anepidu. A monk died because of a snake bite.A lot of monks came to Lord Buddha, they worshiped Lord Buddha and sat down.They asked about the monk who died because of the snake bite.
Lord Buddha answered. Fortunate monks,That monks did not extended his "Meththa" toward the casts of the snake kings.If he did he would't have been bit by a snake.
What are those four casts of snake kings?
One is called "Virupaksha"
One is called "Erapatha"
One is called "Jabyapuththa"
One is called "Kanha Gothamaka"
That monks did not extended his "Meththa" toward these casts of the snake kings.If he did he would't have been bit by a snake.
Fortunate monks, I approve extending Meththa towards these Royal casts of snakes.That will be a security and a protection for you.Also it will be a Meththa chant for you.
Lord Buddha said this afterwards,
May my Meththa be with "Virupaksha" snake cast
May my Meththa be with "Erapatha" snake cast
May my Meththa be with "Jabyapuththa" snake cast
May my Meththa be with "Kanha Gothamaka" snake cast
May my Meththa be with beings without legs.
May my Meththa be with beings with legs.
May my Meththa be with four legged beings.
May my Meththa be with beings with many legs.
May beings without legs cause me no harm.
May beings with legs cause me no harm.
May four legged beings cause me no harm.
May beings with many legs cause me no harm.
May no evil come to all, Living beings and to all beings who have been born May all find comfort.
Lord Buddha is with values above measuring
Dhamma is with values above measuring
Sangha is with values above measuring
Because of polluting "Klehsa" these beings like Snakes,Scorpions,Spiders,Insects and Insects are with measurable values.
I have done protection,I have chanted. May all beings go away from me. I worship Lord Buddha,I worship seven Lord Buddhas of this era.
May the power of truth in these words bring comfort to all!
End of translation.
There's the Ahina Sutta: By a Snake, which includes (I won't quote it all),
I have good will for footless beings,
good will for two-footed beings,
good will for four-footed beings,
good will for many-footed beings.
It's previously mentioned in this answer, which quotes a note that says, "This is one of the few protective charms mentioned in the Pali canon and specifically allowed by the Buddha for monks to use".