\documentclass{book}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage{tabularx}
\begin{document}

\begin{table}[htb]
\begin{tabularx}{\linewidth}{|l|p{1.25cm}|p{1.5cm}|X|}\hline
\multicolumn{1}{|c|}{\textbf{Animal}}
  & \textbf{Hair Colour}
  & \multicolumn{2}{c|}{\textbf{Favourite foods}} \\\hline\hline
Elephant & Gray & Peanuts
  & Unshelled, prepared in Sea Salt, and warmed over hot stone grill \\\cline{3-4}
  &  & Cabbage and Greens
  & Sun dried until lightly browned (2-3 days minimum); 
    seasoned with Hyperchem super feed \\\cline{4-4}
  & & & Boiled to British standard \\\hline\hline
Lion & Yellow & Elephants & Tartare \\\cline{4-4}
& & & Must be served warm, with no trace of 
  buckshot. Gaiminess considered desireable. \\\hline
\end{tabularx} 
\end{table}

alternative

\begin{table}[htb]
\makebox[\linewidth]{%
\begin{tabularx}{1.4\linewidth}{|l|p{1.25cm}|p{1.5cm}|X|}\hline
\multicolumn{1}{|c|}{\textbf{Animal}}
  & \textbf{Hair Colour}
  & \multicolumn{2}{c|}{\textbf{Favourite foods}} \\ \cline{3-4}
  \hline\hline
Elephant & Gray & Peanuts
  & Unshelled, prepared in Sea Salt, and warmed over hot stone grill \\ \cline{3-4}
  &  & Cabbage and Greens
  & Sun dried until lightly browned (2-3 days minimum); 
    seasoned with Hyperchem super feed \\ \cline{4-4}
  & & & Boiled to British standard \\  \cline{4-4}\hline\hline
Lion & Yellow & Elephants & Tartare \\ \cline{4-4}
& & & Must be served warm, with no trace of 
  buckshot. Gaiminess considered desireable. \\  \cline{4-4}\hline
\end{tabularx} 
}
\end{table}

\end{document}