using variable class names instead of lots of if clauses?

I'm trapped right now and don't know an easier solution to this, maybe you can help me out.

I have an Interface called Animal and lots of Animal Classes implementing it. EDIT: The interface must be wrong then:

public interface Animals {
    Integer lifespan = 0;

    public Integer getLifespan();
} 

In a function I get some random animal Object back and I want to get variables of it.

if (animal instanceof GuineaPig) {
            lifespan = ((GuineaPig) animal).getLifespan();
            age = ((GuineaPig) animal).getAge();
            value = ((GuineaPig) animal).getValue();
}
if (animal instanceof Rabbit) {
            lifespan = ((Rabbit) animal).getLifespan();
            age = ((Rabbit) animal).getAge();
            value = ((Rabbit) animal).getValue();
}

Now I need to have if clauses for every animal, there must be an easier way, right? What am I doing wrong?

EDIT2: Full Interface and Classes:

public interface Animals {
final Integer id = 0;
Integer prize = 999999;
Integer value = 0;
Integer age = 0;
Integer lifespan = 0;


String[] colors = {
        "c_bw", "c_w", "c_brw"
};


String name = null;
String finalColor = null;


public String[] getColors();
public Integer getPrize();
public Integer getId();
public Integer getLifespan();
public Integer getAge();
public Integer getValue();
public String getName();
public String setName(String animalName);
public String setFinalColor(String finalColor);
}

class GuineaPig implements Animals {
private final Integer id = 0;
private Integer prize = 10;
private final Integer difficulty = 0; // easy
private final Integer licenceNeeded = 0;
private Integer value = 5;
private Integer age = 0;


private String[] colors = {
    "c_bw", "c_w", "c_brw"
};


private String name = null;
private String finalColor = null;

@Override
public Integer getPrize() {
    return prize;
}


public void setPrize(Integer prize) {
    this.prize = prize;
}

public Integer getDifficulty() {
    return difficulty;
}

public Integer getLicenceNeeded() {
    return licenceNeeded;
}
@Override
public String[] getColors() {
    return colors;
}

public Integer getId() {
    return id;
}

@Override
public Integer getLifespan() {
    return null;
}

public String getName() {
    return name;
}

public String setName(String name) {
    this.name = name;
    return name;
}

public String getFinalColor() {
    return finalColor;
}

public String setFinalColor(String finalColor) {
    this.finalColor = finalColor;
    return finalColor;
}

public Integer getValue() {
    return value;
}

public void setValue(Integer value) {
    this.value = value;
}

public Integer getAge() {
    return age;
}

public void setAge(Integer age) {
    this.age = age;
}
}

class Rabbit implements Animals {
private final Integer id = 1;
private Integer prize = 15;
private Integer lifespan = 30;
private Integer difficulty = 0; // easy
private final Integer licenceNeeded = 1;
private Integer value = 7;
private Integer age = 0;


private String[] colors = {
        "c_b", "c_w", "c_br"
};


private String name = null;
private String finalColor = null;

@Override
public Integer getPrize() {
    return prize;
}

public void setPrize(Integer prize) {
    this.prize = prize;
}

public Integer getDifficulty() {
    return difficulty;
}

public Integer getLicenceNeeded() {
    return licenceNeeded;
}
@Override
public String[] getColors() {
    return colors;
}

public Integer getId() {
    return id;
}

@Override
public Integer getLifespan() {
    return null;
}

public String getName() {
    return name;
}

public String setName(String name) {
    this.name = name;
    return name;
}

public String getFinalColor() {
    return finalColor;
}

public String setFinalColor(String finalColor) {
    this.finalColor = finalColor;
    return finalColor;
}

public Integer getValue() {
    return value;
}

public void setValue(Integer value) {
    this.value = value;
}

public Integer getAge() {
    return age;
}

public void setAge(Integer age) {
    this.age = age;
}
}