Memory allocation of vector of strings

macro_rules! prt {
    ($var: expr) => {
        println!(
            "{:2} {:2} {:p} {:?} {:?}",
            $var.len(),
            $var.capacity(),
            &$var,
            $var.as_ptr(),
            $var
        );
    };
}
fn main() {
    let mut animals = vec![String::from("cat"), String::from("dog")];

    prt!(animals);
    prt!(animals[0]);
    prt!(animals[1]);
    println!();

    animals.extend([String::from("mouse")]);

    prt!(animals);
    prt!(animals[0]);
    prt!(animals[1]);
    prt!(animals[2]);
    println!();

    animals[0].push_str(" is the most dangerous animal");
    prt!(animals);
    prt!(animals[0]);
    prt!(animals[1]);
    prt!(animals[2]);
}

 2  2 0x7ffeaaaa5a98 0x5e44f7653b80 ["cat", "dog"]
 3  3 0x5e44f7653b80 0x5e44f7653bc0 "cat"
 3  3 0x5e44f7653b98 0x5e44f7653be0 "dog"

 3  4 0x7ffeaaaa5a98 0x5e44f7653c20 ["cat", "dog", "mouse"]
 3  3 0x5e44f7653c20 0x5e44f7653bc0 "cat"
 3  3 0x5e44f7653c38 0x5e44f7653be0 "dog"
 5  5 0x5e44f7653c50 0x5e44f7653c00 "mouse"

 3  4 0x7ffeaaaa5a98 0x5e44f7653c20 ["cat is the most dangerous animal", "dog", "mouse"]
32 32 0x5e44f7653c20 0x5e44f7653c90 "cat is the most dangerous animal"
 3  3 0x5e44f7653c38 0x5e44f7653be0 "dog"
 5  5 0x5e44f7653c50 0x5e44f7653c00 "mouse"

• Each string