C#

public void move(IActor actor)
{
    while (true)
    {
        int rand = RandomNumber.GetRandomNumber(1000, 2000);
        Thread.Sleep(rand);

        if (!isPaused)
        {
            lock (_grid)
            {
                IActor bingo = actor.move(this);
                if(bingo != null)
                {
                    Thread thread = new Thread(delegate() { move(bingo); });
                    thread.Start();
                }
            }
        }
    }
}

public IActor move(Field field)
{
    IActor[,] grid = field.Grid;

    //if (grid[CurrentLocation.Y, CurrentLocation.X] == null)
       // return null;

    Location moveTo = MoveToRandomLocation(field);
    if (moveTo != null)
    {
        grid[CurrentLocation.Y, CurrentLocation.X] = null;

        CurrentLocation.X = moveTo.X;
        CurrentLocation.Y = moveTo.Y;

        grid[CurrentLocation.Y, CurrentLocation.X] = this;
    }

    IActor bingo = reproduce(field);
    //if the animal reproduced, return it back to the field
    //so that we can create a new thread for it.
    if(bingo != null)
    {
        return bingo;
    }
    //otherwise return null
    return null
}

public void run()
{
    //the threads have been restarted to accoutn for newborns
    this.RestartThreads = false;
    //iterate through actors on field and start their threads

    //add the newborns from a temp list
    //to the ActoreOnField List and execute the run method

    foreach (IActor actor in actorsOnField)
    {
        Thread t = new Thread(delegate() { move(actor); });
        t.Start();
        RunningThreads.Add(t);
    }
}

public void move(IActor actor)
{
    while (RestartThreads == false)
    {
        int rand = RandomNumber.GetRandomNumber(1000, 2000);
        Thread.Sleep(rand);

        if (!isPaused)
        {
            lock (_grid)
            {
                IActor player = actor.move(this);

                if (player != null)
                {
                    Thread t = new Thread(delegate() { move(player); });
                    t.Start();
                }
            }
        }
    }
}