How to get the name of an object to be written in a sentence?

I tried to find the answer but nothing that I found works... I have an object with properties. There's a separate function that writes a sentence using these propereties. The result I want is "Bob is a 12 years old small turtle.". How can I put the name(not name-properity) of the object into this sentence so it writes 'turtle'?

const turtle = {
  name: "Bob",
  age: 12,
  size: 'small'
}

const writeBio = (animal) => {
  // my attempts:
  let type = animal; // doesn't work, it writes "Bob is a 12 years old small [object Object]."
  let type = Object.keys(animal)[0]; // doesn't work, it writes "...name."
  let type = animal.constructor.name;  // doesn't work, it writes "...Object."
  const {name, size, age} = animal;
  console.log(`${name} is a ${age} years old ${size} ${type}.`);
}

writeBio(turtle);