The bovine animal (toy?) in this page is said to be a "Water buffalo figurine from Harappa." Let us call this Figure [A].
However, comparing with other Indus humpless ox/bull figures make the buffalo ID questionable. Figure [A] rather seems like an ox figurine, with its head raised when a rope is pulled by a cart man or while ploughing. Very similar to this is the bullock cart (not a buffalo cart) shown in http://www.harappa.com/figurines/2.html
Considering water buffalos in Indus seals, the semi-circular curves of Indian buffalo horns are very noticeable. And, these type of horns are lacking from Figure [A] and the bullock cart shown above.
The cross-span of the Indus buffalo horns is wider than the span of ox horns, and buffalo horns start out in a much more flatter fashion than those of Figure [A] or the cart bullock. For example, look at the Indus water buffalo figurine at the lower row which is at the left most side to the viewer. Again, the Figure [A] horns are not compatible with these buffalo horns.
Real Indian buffalos:
Let's take a look at the seven pictures of Indus (unhumped, or zebu with hump) bull/ox figurines. The horns of Figure [A] bovine look closer to these ox horn characteristics.
(5, 6 & 7) http://www.argainc.com/Argainc/10c1.asp?cod=4000152
Indus Valley (Harappa) bull 2800 B.C. cm. 16 x 28 (in. 6.3 x 11.4)
In the other direction, buffalos have been taken to be a zebu bull. Let us look at an example. The elliptical (almost semi-curcular) curve of the buffalo horns are quite different from those of the zebu bovines shown above. http://www.hindu.com/2008/01/13/stories/2008011355961800.htm
"Jallikattu,” which is bull-baiting or bull fighting, is an ancient Dravidian tradition that was practised about 4,000 years ago during the Indus Valley civilisation.
A well-preserved seal found at Mohenjodaro in the 1930s attests to this, according to Iravatham Mahadevan, a specialist in Indus and Brahmi scripts.
The animal in the Indus seal from Mohenjo Daro (M-312 in Corpus of Indus seals and inscriptions) given in the article by T. S. Subramanian ("Bull-baiting of yore", The Hindu, January 13, 2008) is most likely a water buffalo, not a taurus bull. Further Alf Hiltebeitel ("The Indus Valley 'Proto-Siva', Reexamined through Reflections on the Goddess, the Buffalo, and the Symbolism of Vaahanas." Anthropos 73:5-6 (1978):767-97 ) thinks the animal involved is a wild buffalo. pg. 772, "Finally it is likely that the horns are not only those of the buffalo but of the wild buffalo. Other Indus Valley seals show the animal in "truculent" poses, one buffalo in particular (Mackay, no. 510) having "thrown" five human figures about him. The upward curve of the horns which characterises the buffalo on all these seals portrays the animal at his most aggressive potential."
Photo Credits: Thanks and due credits are given to those make these pictures available in the web for scholarly research. The referring URL links are provided inside this post near the pictures.