HAROLD'S TAIL

Written and illustrated by John Bemelmans Marciano

Viking. 160 pp. $15.99; ages 8-12

THE MAYOR OF CENTRAL PARK

Written by Avi. Illustrated by Brian Floca

HarperCollins. 193 pp. $15.99; ages 8-12

The world of rats and squirrels, above the heads and below the feet of the human population of New York City, is illuminated in two new books that discover rivalries and alliances within the critters' camps. A rat mafia takes over the squirrels' Central Park in Avi's The Mayor of Central Park, but even in war, inter-rodent love can still bloom. In Harold's Tail, written and illustrated by John Bemelmans Marciano, the grandson of "Madeline" creator Ludwig Bemelmans, one gray squirrel finds shelter and companionship with a nest of rats after he discovers that there's very little separating the species besides a people-pleasing tail.

Marciano's Harold lives a sheltered life, tucked away in a tiny park, until one day a rat named Sidney bets him that, without his bushy tail, his beloved human visitors wouldn't treat him so kindly. They shave off Harold's tail fur, paste it to the rat's rear, and wait for the reaction. Not surprisingly, Harold is reviled, while Sidney gets all the free nuts and crumbs he can eat. As one of the most lively characters, Sidney is also featured in perhaps the most amusing of Marciano's illustrations: the bloated rat laid flat on his back with an over-stuffed stomach.

The tale, a version of Mark Twain's oft-adapted The Prince and the Pauper, follows Harold as he makes his way through the city, detested by all and in despair until he finds a group of rats to take him in. Although it's a sweetly told story, promoting the virtues of tolerance and adventurousness, Harold's wooden narrative voice keeps his character from springing fully to life. At the moment of his greatest triumph -- providing food for the rats who had helped him so generously -- Harold stiffly pronounces, "I'd never felt prouder. After feeling helpless for so long, having to be taught everything, it felt good to show that I knew something too." However, Marciano's illustrations are nicely articulated, capturing each animal's unique characteristics.

The Mayor of Central Park, the latest from prolific author Avi, is a clever and thrilling tale of a turf war over New York's most famous park. Set in 1900, the story of the rat mafia's hostile takeover is narrated in the sly, wisecracking voice of a hardboiled journalist. The characters are vivid and eccentric: There's Oscar Westerwit, the titular mayor, self-satisfied and content as the big squirrel in a little tree; Big Daddy Duds, the boss of the rats, who adores baseball, diamonds and himself; Maud, the boss's daughter, whose large heart and cute face put her at the center of every romantic entanglement; and Uriah Pilwick, Duds's possum deputy who may not be the dull-witted heavy that he seems.

One fine day in May, Oscar discovers that the star pitcher for his baseball team is missing; soon after, the rats invade the park, looking for rich new territory to exploit. With trees being felled and all the peaceful denizens of the park uprooted from their homes, Oscar must find a way to win back the park -- along with Maud's heart. The story is embellished with cunning period detail, although the history lessons can be stilted at times. For instance, in the midst of a conversation about the missing player, Oscar lectures, "Guys like us have been around here long before 1857 when the park was built; long before the Dutch showed up in 1612. Long even before the Lenape Indians named this island Manna-hata." But such passages rarely hamper the swiftness of the plot.

Avi's prose displays an obvious love of language, including ample alliteration ("Frustrated as a floppy fish in a frying pan"), snappy dialogue ("I'd kinda like to catch the cash." "Sure thing, Bigalow, but if I chop you coin, you got to swear to never noodle near my daughter no more") and inventive descriptions ("The moon might have been high in the sky as it moved to midnight, but Oscar's mood was hugging his ankles").

This New York is brash, energetic and wittily translated to fit Avi's anthropomorphic world, while Brian Floca's full-page illustrations skillfully render both the characters and their park. In his elegantly detailed pencil drawings, a battalion of rats, armed and at attention, fills Bethesda Fountain Terrace (the angel of the fountain, of course, is here a squirrel); in another, the nattily attired Oscar hatches a plot in the dim bar of the Rock and Mole Cafe.

Both Harold's Tail and The Mayor of Central Park imaginatively address the conundrum of urban wildlife. What's really the difference between the despised rat and the beloved squirrel, other than the scaly and serpentine tail of one and the bouncy and bushy rump of the other? These books prove the point that you can't judge a critter by its fur. *

Andrea Thompson is on the staff of the New Yorker.