Research Article | Open Access

Chenglin Li, Zhangguo Hong, "Global Existence of Classical Solutions to a Three-Species Predator-Prey Model with Two Prey-Taxes", *Journal of Applied Mathematics*, vol. 2012, Article ID 702603, 12 pages, 2012. https://doi.org/10.1155/2012/702603

# Global Existence of Classical Solutions to a Three-Species Predator-Prey Model with Two Prey-Taxes

**Academic Editor:**Alain Miranville

#### Abstract

We are concerned with three-species predator-prey model including two prey-taxes and Holling type II functional response under no flux boundary condition. By applying the contraction mapping principle, the parabolic Schauder estimates, and parabolic estimates, we prove that there exists a unique global classical solution of this system.

#### 1. Introduction

In addition to random diffusion of the predator and the prey, the spatial-temporal variations of the predators’ velocity are directed by prey gradient. Several field studies measuring characteristics of individual movement confirm the basis of the hypothesis about the dependence of acceleration on a stimulus [1]. Understanding spatial and temporal behaviors of interacting species in ecological system is a central problem in population ecology. Various types of mathematical models have been proposed to study problem of predator-prey. Recently, the appearance of prey-taxis in relation to ecological interactions of species was studied by many scholars, ecologists, and mathematicians [2–5].

In [2] the authors proved the existence and uniqueness of weak solutions to the two-species predator-prey model with one prey-taxis. In [3], the author extended the results of [2] to an reaction-diffusion-taxis system. In [4], the author proved the existence and uniqueness of classical solutions to this model. In this paper, we deal with three-species predator-prey model with two prey-taxes including Holling type II functional response as follows: where is a bounded domain in is an integer) with a smooth boundary ; and represent the densities of the predator and prey, respectively; the positive constants , , and are the diffusion coefficient of the corresponding species; the positive constants represent the death rate of the predator, the carrying capacity of prey, the prey intrinsic growth rate, the half-saturation constant, the conversion rate, the time spent by a predator to catch a prey, the manipulation time which is a saturation effect for large densities of prey, the density of prey necessary to achieve one-half the rate, respectively; the predators are attracted by the preys, and the positive constant denotes their prey-tactic sensitivity. The parts and of the flux are directed toward the increasing population density of and , respectively. In this way, the predators move in the direction of higher concentration of the prey species.

The aim of this paper is to prove that there is a unique classical solution to the model (1.1). It is difficult to deal with the two prey-taxes terms. To get our goal we employ the techniques developed by [6, 7] to investigate.

Throughout this paper we assume that The assumptions that for and for have a clear biological interpretation [2]: the predators stop to accumulate at given point of after their density attains a certain threshold value and the prey-tactic sensitivity and vanishes identically when .

Throughout this paper we also assume that Denote by ( is integer, ) the space of function with finite norm [8]: where We denote by the space of functions with norm

The main result of this paper is as follows.

Theorem 1.1. *Under assumptions (1.2) and (1.3), for any given there exists a unique solution of the system (1.1), where . Moreover,
**
for any and .*

This paper is organized as follows. In Section 2, we present some preliminary lemmas that will be used in proving later theorem. In Section 3, we prove local existence and uniqueness to system (1.1). In Section 4, we prove global existence to system (1.1).

#### 2. Some Preliminaries

For the convenience of notations, in what follows we denote various constants which depend on by , while we denote various constants which are independent of by .

Lemma 2.1. *Let . Then
**
where .*

*Proof. *Using the definition of Hölder norm, we have
which yields that
Therefore,

We now consider the following nonlinear parabolic problem: By the parabolic maximum principle, we have .

Lemma 2.2. *Let
**
Then, under assumptions (1.2) and (1.3), there exists a unique nonnegative solution of the nonlinear problem (2.5) for small which depends on .*

*Proof. *This proof is similar to that of Lemma 2.1 in [4]. For reader’s convenience we include the proof here. We will prove by a fixed point argument. Let us introduce the Banach space of function with norm and a subset , where . For any , we define a corresponding function , where satisfies the equations
By , we have
By the parabolic Schauder theory, this yields that there exists a unique solution to (2.7) and
where is some constant which depends only on . For any function , by Lemma 2.1 and combining (2.9), if is sufficiently small ( depends only on ), then we have
Therefore, and maps into itself. We now prove that is contractive. Take in , and set . Then, it follows from (2.7) that solves the following systems:
where
By and conditions of Lemma 2.2, it is easy to check that
Using the assumption and the -estimate, we have
For any , by using Sobolev embedding ( if we take sufficiently large), we have
Then, noting , we can easily check that [4]
Taking small such that , we conclude from (2.16) that is contractive in . Therefore has a unique fixed point , which is the unique solution to (2.5). Moreover, we can raise the regularity of to by using the parabolic Schauder estimates.

#### 3. Local Existence and Uniqueness of Solutions

In this section, we will prove Theorem 3.1 which show that system (1.1) has a unique solution as done in [6, 7].

Theorem 3.1. *Assume that (1.2) and (1.3) hold, then there exists a unique solution of the system (1.2) for small which depends on
**
Furthermore, .*

*Proof. *We will prove the local existence by a fixed point argument again. Introducing the Banach space of the function , we define the norm
and a subset
where
For any , we define correspondingly function by , where satisfies the equations
By (3.5), , assumption (1.3), and the parabolic Schauder theory, we have that there exists a unique solution to (3.5) and
Similarly,
Moreover, by parabolic maximum principle, we have
Similarly, by using Lemma 2.2, from (3.6) we can conclude that there exists a unique solution satisfying
and by parabolic maximum principle we have in . From (3.7), (3.8), and (3.10), we have
For any function , using Lemma 2.1 we get
From (3.11) and (3.12), if is sufficiently small we have
which yields . Therefore, maps into itself.

Next, we can prove that is contractive as done in the proof of Lemma 2.2 in if we take sufficiently small. By the contraction mapping theorem has a unique fixed point , which is the unique solution of (1.1). Moreover, we can raise the regularity of to by using the parabolic Schauder estimates.

#### 4. Global Existence

First we establish some a priori estimates to (1.1).

Lemma 4.1. *Suppose that is a solution to the system (1.1), then there holds
*

*Proof. *It follows from (1.1) that
Obviously, is a subsolution to (4.2). Using the maximum principle, we get . Similarly, we have and .

On the other hand, it follows from model (1.1) that
which implies that is a subsolution to problem (4.3). Hence we have . Similarly, we get . This completes the proof of Lemma 4.1.

Lemma 4.2. *Suppose that is a solution to the system (1.1), then for any there holds
*

*Proof. *Multiplying the first equation of (1.1) by , integrating over , using the no-flux boundary condition, and noting , we get
For , we get
Therefore
Using Gronwall’s Lemma, we have
Therefore, for , we have
Obviously, we have
This completes the proof of Lemma 4.2.

Lemma 4.3. *Suppose that is a solution to the system (1.1), then for any there holds
*

*Proof. *Note that the second equation of (1.1) can be rewritten as follows:
where .

By the parabolic -estimate, we have
Using the Sobolev embedding theorem (taking ), we get
Similarly, we can obtain
It follows from the first equation of (1.1) that
where
Using the parabolic -estimates again, we have
This completes the proof of Lemma 4.3.

Lemma 4.4. *Suppose that is a solution to the system (1.1), then there holds
*

*Proof. *Using the Sobolev embedding theorem (taking ) and Lemma 4.3, we have
Using (4.20) and the Schauder estimates to the second and third equation of model (1.1), we have
Applying the parabolic Schauder estimate to (4.16) and using (4.21), we have
This completes the proof of Lemma 4.4.

Therefore, we can extend the local solution established in Theorem 3.1 to all , as done in [6, 7]. Namely, we have the following.

Theorem 4.5. *Under assumptions (1.2) and (1.3), there exists a unique solution of the system (1.2) for any given . Moreover,
**
for any and . *

#### Acknowledgments

The authors are grateful to the referees for their helpful comments and suggestions. This work is supported by the Fundamental Research Funds for the Central Universities (no. XDJK2009C152).

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#### Copyright

Copyright © 2012 Chenglin Li and Zhangguo Hong. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.